3 pages long, single-spaced, font 12, Times New Roman.
A fourth page should list the references cited in the essay.
hree-page essay should devote about 1/3 to the underlying chemistry (as developed
in the lectures and suggested readings), ( about) 1/3 to present applications, and (about) 1/3 to
suggest how the situation may change in the future, adding any personal views or insights
(as appropriate).
The first 1/3, should focus on what is already known and been reported/published.
The second 1/3 should focus on present applications. What is the atom/molecule/process being used
for today. Put simply, what are the business/market implications? By any measure, the chemical
industry is the largest World-wide. Almost every product you use in everyday life or consume at
breakfast/lunch/dinner is a product produced by the chemical industry. Materials to construct buildings
and bridges, fabricate plastics and drugs, airplanes and space ships , … and now ventilators, are produced
industrially from “chemicals” found in Nature. And, of course, the fuels used in cars and to heat
your home all derive from chemical substances processed in refineries. It is this “relevance” that I
ask you to discuss.
The third section should then focus on what might be the future for the atom/molecule/process
you choose to discuss. This section is usually the one that separates “the women from the girls.” This
is because you will have to do some “digging,” checking the business section of the Wall Street
Journal, the New York Times, Bloomberg, …. for educated projections.
C
HE 102: LECTURE 1 Get
tin
g
S
t
art
ed.
1. “The turning-point to the spread of agriculture in the Old World was almost certainly
the occurrence of two forms of w
heat
with a large, full head of seeds.
Before 8000 BC
wheat was not the luxuriant plant it is today; it was merely one of many wild grasses
that spread throughout the Middle East. By some genetic accident, the wild wheat
crossed with natural goat grass and formed a fertile hybrid.”
Bronowski, The Ascent of Man, p.65
This genetic variety is today known as Emmer wheat.
Today, advances in genetic engineering allow variations to be incorporated into the
genetic map of plants to improve their resistance, for example, to insects.
Today, the “seed industry” is a multi-billion dollar business.
2. Discovery of this grain led to the
transition
from “hunter gatherer” societies
(the Bakhtiari in Persia, the Plains Indian tribes) to stable, stationary agricultural
societies. This transition occurred independently in (at least) eight lo
cations
across Asia and South America.
In addition to using wheat to make bread, a new beverage was brewed, beer.
The earliest evidence of beer from barley/wheat is a 3900 year old brew
from Sumeria (not available).
Wheat beers available today (which have some amount of barley), are
the Belgian beer Hoegaarden, and the US Blue Moon.
With the formation of permanent communities, social structures evolved and craftsmen could be supported. Trade routes were established whereby metals (
copper
, tin,
gold
) and
precious
stones (lapis lazuli) were transported over ever-increasing distances.
The
Bronze
Age
is the time period when people made
tools
from an
alloy
called
bronze
(a mixture of copper and tin). Bronze was first used in Mesopotamia (Iraq, Kuwait, the eastern parts of Syria, Southeastern Turkey) around 3300 BC.
In Western Europe, the Bronze Age lasted from about 2000 BC until 800 BC.
3. There are twelve
elements
that have been known since antiquity:
Copper (Cu), Lead (Pb),
Go
ld (Au),
Si
lver (Ag),
Iron
(Fe),
Carbon(C),
Ti
n(
Sn
), Sulfur (S),
Mercury
(Hg), Zinc (Zn),
Arsenic (As), Antimony (Sb)
Today, all are important commercially/industrially, and several are traded
daily in the commodity markets.
3. Elements (92 naturally occurring on Earth) are classified into metals (e.g. Cu)
and
nonmetals
(e.g., S).
Chemical
ly, they are referred to as atoms. Sulfur and Carbon are nonmetals, the
rest on the above list are metals.
Marriages of atoms yield compounds. These compounds may be either molecular or
ionic (consisting of charged atoms). Examples of molecular compounds follow.
Water (H2O)
[ The most essential molecule on planet Earth. More than 70 percent of Earth is
covered in water and, coincidentally, about 70 percent of the human body is made
up of water. Essential for the bio
chemistry
of life. ]
(oxygen in red,
hydrogen
in white)
N
atural gas, which consists primarily of methane, CH4 , is a fossil fuel.
[Methane in the Earth’s atmosphere is a strong greenhouse gas with a global
warming potential (GWP) 104 times greater than CO2 in a 20-year time
frame; methane is not as persistent a gas as CO2 (assuming no change in
carbon
sequestration rates) and tails off to about GWP of 28 for a 100-year time frame.]
(carbon in green, hydrogen in white)
Examples of ionic compounds follow.
Table salt, the mineral Halite (a mineral is the name in Geology for a compound) is
formed from the metal
sodium
(Na) and the non-metal chlorine (Cl).
[Salt plays a crucial role in maintaining human health. It is the main source of sodium
and chloride ions in the human diet.
Sodium
is essential for nerve and muscle function
and is involved in the regulation of fluids in the body. Sodium also plays a role in the
body’s control of blood pressure and volume. Salt is also used for seasoning and
preserving food. In antiquity, important cities grew up in the vicinity of salt mines,
notably the Wieliczka Salt Mine which today is a suburb of Kraków,
Po
land.]
Cr
ystal structure: sodium ions in purple, chlorine ions in green.
Iron oxide, Fe2O3 obtained from the mineral Hematite, is a common
iron
oxide,
widespread in rocks and soils. Hematite is colored black to
steel
or
silver
-gray,
brown to reddish-brown, or red. It is mined as the main ore of iron. Crystal structure
is below (iron in purple, oxygen in red).
A more exotic example of a compound is the precious stone lapis lazuli, obtained
from the mineral Lazurite, formula
(Na,Ca) 8 (
Al
SiO4)6 (S,SO4,Cl)1-2)
This mineral is on the death mask (eyebrows and “hat”) of Tutankhamum, the 18th dynasty Egyptian Pharaoh (1332-1323 BC).
It is also the “blue” in the painting by the Dutch master, Johannes Vermeer, “Girl with a
Pearl Earring” (1665), using ultramarine, a natural pigment made from lapis lazuli.
It is almost certain that the only source of lapis lazuli for ancient Egypt was Badakshan in northeastern Afghanistan. Lazurite has been
extracted
from the Sar-i Sang mine in Afghanistan since the 7th Millennium BC. The stone then reached Egypt along the trade routes. Today, driving the ~2800 miles from Kabul, Afghanistan to Cairo, Egypt takes ~47
hours. Camels were used then. Camels can run at 25 mph for long periods, a journey of
~ 3-4 months.
METALS
The following is a Wikipedia website giving a comprehensive discussion of the
properties of metals. There is far more here than you need for this course, but
I would recommend that you read the
material
to gain some appreciation for the
range of properties and applications of metals.
NOTE: Should you decide to write your first essay on a metal, this would be a good
place to start. The literature references are listed at the end of the site.
Metal
From Wikipedia, the free encyclopedia
Jump to navigation
Jump to s
earch
Not to be confused with
Medal
,
Meddle
, or
Mettle
.
This article is about metallic materials. For other uses, see
Metal (disambiguation)
.
Iron,
show
n here as fragments and a 1 cm3 cube, is an example of a
chemical element
that is a metal
A metal in the form of a gravy boat made from
stainless steel
, an alloy largely composed of iron, carbon, and
chromium
A metal (from
Greek
μέταλλον métallon, “mine, quarry, metal”) is a material that, when freshly prepared, polished, or fractured, shows a
lustrous
appearance, and conducts
electricity
and heat relatively well.
Metals
are typically
malleable
(they can be hammered into thin sheets) or
ductile
(can be drawn into wires). A metal may be a chemical element such as iron; an alloy such as stainless steel; or a molecular compound such as
polymeric
sulfur
nitride
.
In physics, a metal is generally regarded as any substance capable of conducting electricity at a temperature of
absolute zero
.
[1]
Many elements and compounds that are not normally classified as metals become metallic under high pressures. For example, the nonmetal
iodine
gra
dual
ly becomes a metal at a pressure of between 40 and 170 thousand times
atmospheric pressure
. Equally, some materials regarded as metals can become nonmetals. Sodium, for example, becomes a nonmetal at pressure of just under two million times atmospheric pressure.
In chemistry, two elements that would otherwise qualify (in physics) as brittle metals—
arsenic
and
antimony
—are commonly instead recognised as
metalloid
s
, on account of their predominately non-metallic chemistry. Around 95 of the 118 elements in the
periodic table
are metals (or are likely to be such). The number is inexact as the boundaries between metals, nonmetals, and metalloids fluctuate s
light
ly due to a lack of universally accepted definitions of the categories involved.
In
astrophysics
the term “metal” is cast more widely to refer to all chemical elements in a star that are heavier than the lightest two, hydrogen and
helium
, and not just traditional metals. A star
fuses
lighter atoms, mostly hydrogen and helium, into heavier atoms over its lifetime. Used in that sense, the
metallicity
of an astronomical object is the proportion of its matter made up of the heavier chemical elements.
[2]
Metals, as chemical elements, comprise 25% of the Earth’s crust and are present in many aspects of modern life. The strength and resilience of some metals has led to their frequent use in, for example, high-rise building and bridge
construction
, as well as most vehicles, many
home appliances
, tools, pipes, and railroad tracks.
Precious metals
were historically used as
coinage
, but in the modern era,
coinage metals
have extended to at least 23 of the chemical elements.
[3]
The history of
refine
d metals is thought to begin with the use of copper about 11,000 years ago.
Gold
, silver, iron (as meteoric iron),
lead
, and
brass
were likewise in use before the first known appearance of bronze in the 5th millennium BCE. Subsequent developments include the production of early forms of steel; the discovery of sodium—the first
light metal
—in 1809; the rise of modern
alloy steel
s; and, since the end of World War II, the development of more sophisticated alloys.
Contents
·
1Properties
· 1.1
Form and structure
· 1.2
Electrical and thermal
·
1.3Chemical
·
2Periodic table distribution
·
3Alloys
·
4
Categories
· 4.1
Ferrous and non-
ferrous
metals
· 4.2
Brittle metal
· 4.3
Refractory metal
· 4.4
White metal
· 4.5
Heavy and
light metals
· 4.6
Base,
noble
and
precious metal
s
·
5Lifecycle
· 5.1
Formation
· 5.2
Abundance and occurrence
· 5.3
Extraction
· 5.4
Uses
· 5.5
Recycling
·
6Biological interactions
·
7History
· 7.1
Prehistory
· 7.2
Antiquity
· 7.3
Middle Ages
· 7.4
The Renaissance
· 7.5
Light metals
· 7.6
The age of steel
· 7.7
The last stable metallic elements
· 7.8
Post-World War II developments
· 7.8.1
Superalloys
· 7.8.2
Transcurium metals
· 7.8.3
Bulk metallic glasses
· 7.8.4
Shape-memory alloys
· 7.8.5
Quasicyrstalline alloys
· 7.8.6
Complex metallic alloys
· 7.8.7
High entropy alloys
· 7.8.8MAX phase alloys
·
8See also
·
9Notes
·
10References
·
11Further reading
·
12External links
Properties
Form and structure
Gallium
crystals
Metals are shiny and lustrous, at least when freshly prepared, polished, or fractured. Sheets of metal thicker than a few micrometres appear opaque, but
gold leaf
transmits green light.
The solid or liquid state of metals largely originates in the capacity of the metal atoms involved to readily lose their outer shell electrons. Broadly, the forces holding an individual atom’s outer shell electrons in place are weaker than the attractive forces on the same electrons arising from interactions between the atoms in the solid or liquid metal. The electrons involved become delocalised and the atomic structure of a metal can effectively be visualised as a collection of atoms embedded in a cloud of relatively mobile electrons. This type of interaction is called a
metallic bond
.
[4]
The strength of metallic bonds for different elemental metals reaches a maximum around the center of the
transition metal
series, as these elements have large numbers of delocalized electrons.
[n 1]
Although most elemental metals have higher
densities
than most nonmetals,[4] there is a wide variation in their densities,
lithium
being the least dense (0.534 g/cm3) and
osmium
(22.59 g/cm3) the most dense. Magnesium,
aluminium
and
titanium
are light metals of significant commercial importance. Their respective densities of 1.7, 2.7 and 4.5 g/cm3 can be compared to those of the older structural metals, like iron at 7.9 and copper at 8.9 g/cm3. An iron ball would thus weigh about as much as three aluminium balls.
A metal rod with a hot-worked eyelet.
Hot-working
exploits the capacity of metal to be plastically deformed.
Metals are typically malleable and ductile, deforming under
stress
without
cleaving
.[4] The nondirectional nature of metallic bonding is thought to contribute significantly to the ductility of most metallic solids. In contrast, in an ionic compound like table salt, when the planes of an
ionic bond
slide past one another, the resultant change in location shifts ions of the same charge into close proximity, resulting in the
cleavage
of the crystal. Such a shift is not observed in a
covalently bonded
crystal, such as a diamond, where fracture and crystal fragmentation occurs.
[5]
Reversible
elastic deformation
in metals can be described by
Hooke’s Law
for restoring forces, where the stress is linearly proportional to the
strain
.
Heat or forces larger than a metal’s
elastic limit
may cause a permanent (irreversible) deformation, known as
plastic deformation
or
plasticity
. An applied force may be a
tensile
(pulling) force, a
compressive
(pushing) force, or a
shear
,
bending
or
torsion
(twisting) force. A temperature change may affect the movement or displacement of
structural defects
in the metal such as
grain boundaries
,
point vacancies
,
line and screw dislocations
,
stacking faults
and
twins
in both
crystalline
and
non-crystalline
metals. Internal
slip
,
creep
, and
metal fatigue
may ensue.
The atoms of metallic substances are
typically arranged
in one of three common
crystal structures
, namely
body-centered cubic
(bcc),
face-centered cubic
(fcc), and
hexagonal close-packed
(hcp). In bcc, each atom is positioned at the center of a cube of eight others. In fcc and hcp, each atom is surrounded by twelve others, but the stacking of the layers differs. Some metals adopt different structures depending on the temperature.
[6]
·
Body-centered cubic crystal structure, with a 2-atom
unit cell
, as found in e.g. chromium, iron, and tungsten
·
Face-centered cubic crystal structure, with a 4-atom unit cell, as found in e.g. aluminium, copper, and gold
·
Hexagonal close-packed crystal structure, with a 6-atom unit cell, as found in e.g. titanium,
cobalt
, and
zinc
The unit cell for each crystal structure is the smallest group of atoms which has the overall symmetry of the crystal, and from which the entire crystalline lattice can be built up by repetition in three dimensions. In the case of the body-centered cubic crystal structure shown above, the unit cell is made up of the central atom plus one-eight of each of the eight corner atoms.
Electrical and thermal
The energy states available to electrons in different kinds of solids at
thermodynamic equilibrium
.
Here, height is energy while width is the
density of available states
for a certain energy in the material listed. The shading follows the
Fermi–Dirac distribution
(black = all states filled, white = no state filled).
The
Fermi level
EF is the energy level at which the electrons are in a position to interact with energy levels above them. In metals and
semimetals
the Fermi level EF lies inside at least one band of energy states.
In
insulators
and
semiconductors
the Fermi level is inside a
band gap
; however, in semiconductors the bands are near enough to the Fermi level to be
thermally populated
with electrons or
holes
.
The electronic structure of metals means they are relatively good
conductors of electricity
. Electrons in matter can only have fixed rather than variable energy levels, and in a metal the energy levels of the electrons in its electron cloud, at least to some degree, correspond to the energy levels at which electrical conduction can occur. In a semiconductor like
silicon
or a nonmetal like sulfur there is an energy gap between the electrons in the substance and the energy level at which electrical conduction can occur. Consequently, semiconductors and nonmetals are relatively poor conductors.
The elemental metals have electrical conductivity values of from 6.9 × 103 S/cm for
manganese
to 6.3 × 105 S/cm for silver. In contrast, a
semiconducting
metalloid such as
boron
has an electrical conductivity 1.5 × 10−6 S/cm. With one exception, metallic elements reduce their electrical conductivity when heated.
Plutonium
increases its electrical conductivity when heated in the temperature range of around −175 to +125 °C.
Metals are relatively good
conductors of heat
. The electrons in a metal’s electron cloud are highly mobile and easily able to pass on heat-induced vibrational energy.
The contribution of a metal’s electrons to its heat capacity and thermal conductivity, and the electrical conductivity of the metal itself can be calculated from the
free electron model
. However, this does not take into account the detailed structure of the metal’s ion lattice. Taking into account the positive potential caused by the arrangement of the ion cores enables consideration of the
electronic band structure
and
binding energy
of a metal. Various mathematical models are applicable, the simplest being the
nearly free electron model
.
Chemical
Metals are usually inclined to form cations through electron loss.[4] Most will react with oxygen in the air to form
oxides
over various timescales (
potassium
burns in seconds while iron
rusts
over years). Some others, like
palladium
,
platinum
and gold, do not react with the atmosphere at all. The oxides of metals are generally
basic
, as opposed to those of nonmetals, which are
acidic
or neutral. Exceptions are largely oxides with very high
oxidation
states
such as CrO3, Mn2O7, and OsO4, which have strictly acidic reactions.
Pa
inting
,
anodizing
or
plating
metals are good ways to prevent their
corrosion
. However, a more
reactive
metal in the
electrochemical series
must be chosen for coating, especially when chipping of the coating is expected. Water and the two metals form an
electrochemical cell
, and if the coating is less reactive than the underlying metal, the coating actually promotes corrosion.
Periodic table distribution
In chemistry, the elements which are usually considered to be metals under ordinary conditions are shown in yellow on the periodic table below. The elements shown as having unknown properties are likely to be metals. The remaining elements are either metalloids (B, Si, Ge, As, Sb, and Te being commonly recognised as such) or nonmetals. Astatine (
At
) is usually classified as either a nonmetal or a metalloid; it has been predicted to be a metal. It is here shown as a metalloid.
hide
· v
· t
· e
Metals–metalloids–nonmetals in the
periodic table
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Group
→
↓
Period
1
H
He
2
Li
Be
B
C
N
O
F
Ne
3
Na
Mg
Al
Si
P
S
Cl
Ar
4
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
5
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
6
Cs
Ba
La
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
7
Fr
Ra
Ac
Th
Pa
U
Np
Pu
Am
Cm
Bk
Cf
Es
Fm
Md
No
Lr
Rf
Db
Sg
Bh
Hs
Mt
Ds
Rg
Cn
Nh
Fl
Mc
Lv
Ts
Og
Metal Metalloid Nonmetal Unknown properties
Background color shows metal–metalloid–nonmetal trend in the periodic table
Alloys
Main article:
Alloy
Samples of
babbitt metal
, an alloy of tin, antimony and copper, used in bearings to reduce friction
An alloy is a substance having metallic properties and which is composed of two or more elements at least one of which is a metal. An alloy may have a variable or fixed composition. For example, gold and silver form an alloy in which the proportions of gold or silver can be freely adjusted; titanium and silicon form an alloy Ti2Si in which the ratio of the two components is fixed (also known as an
intermetallic compound
).
A sculpture cast in
nickel
silver
—an alloy of copper, nickel, and zinc that looks like silver
Most pure metals are either too soft, brittle or chemically reactive for practical use. Combining different ratios of metals as alloys modifies the properties of pure metals to produce desirable characteristics. The aim of making alloys is generally to make them less brittle, harder, resistant to corrosion, or have a more desirable color and
luster
. Of all the metallic alloys in use today, the alloys of iron (steel, stainless steel,
cast iron
,
tool steel
, alloy steel) make up the largest proportion both by quantity and commercial value. Iron alloyed with various proportions of carbon gives low, mid and high carbon steels, with increasing carbon levels reducing ductility and toughness. The addition of silicon will produce cast irons, while the addition of chromium, nickel and
molybdenum
to carbon steels (more than 10%) results in stainless steels.
Other significant metallic alloys are those of aluminium, titanium, copper and
magnesium
. Copper alloys have been known since prehistory—bronze gave the Bronze Age its name—and have many applications today, most importantly in electrical wiring. The alloys of the other three metals have been developed relatively recently; due to their chemical reactivity they require
electrolytic
extraction processes. The alloys of aluminium, titanium and magnesium are valued for their high strength-to-weight ratios; magnesium can also provide
electro
magnetic
shielding
.[
citation needed
] These materials are ideal for situations where high strength-to-weight ratio is more important than material cost, such as in aerospace and some automotive applications.
Alloys specially designed for highly demanding applications, such as
jet engines
, may contain more than ten elements.
Categories
Metallic elements
Alkali metals
· lithium
· sodium
· potassium
· rubidium
· caesium
· francium
Alkaline earth metals
· beryllium
· magnesium
· calcium
· strontium
· barium
· radium
Transition metal
s
· scandium
· titanium
· vanadium
· chromium
· manganese
· iron
· cobalt
· nickel
· copper
· yttrium
· zirconium
· niobium
· molybdenum
· technetium
·
ruthenium
·
rhodium
· palladium
· silver
· hafnium
· tantalum
· tungsten
· rhenium
· osmium
·
iridium
· platinum
· gold
· rutherfordium
· dubnium
· seaborgium
· bohrium
· hassium
Post-transition metals
· aluminium
· zinc
· gallium
·
cadmium
·
indium
· tin
·
mercury
· thallium
· lead
·
bismuth
· polonium
· copernicium
Lanthanides
· lanthanum
· cerium
· praseodymium
·
neodymium
· promethium
· samarium
· europium
· gadolinium
· terbium
· dysprosium
· holmium
· erbium
· thulium
· ytterbium
· lutetium
Actinides
· actinium
·
thorium
· protactinium
·
uranium
· neptunium
·
plutonium
· americium
· curium
· berkelium
· californium
· einsteinium
· fermium
· mendelevium
· nobelium
· lawrencium
Elements which are possibly metals
· meitnerium
· darmstadtium
· roentgenium
· nihonium
· flerovium
· moscovium
· livermorium
· tennessine
· oganesson
Elements which are sometimes considered metals
· germanium
· arsenic
· selenium
· antimony
· tellurium
· astatine
· t
· e
See also:
Names for sets of chemical elements
Metals can be categorised according to their physical or chemical properties. Categories described in the subsections below include ferrous and
non-ferrous
metals; brittle metals and
refractory metals
;
heavy
and light metals; and
base
, noble, and precious metals. The Metallic elements table in this section categorises the elemental metals on the basis of their chemical properties into
alkali
and
alkaline earth
metals; transition and
post-transition
metals; and
lanthanides
and
actinides
.
Other categories
are possible, depending on the criteria for inclusion. For example, the
ferromagnetic
metals—those metals that are magnetic at room temperature—are iron, cobalt, and nickel.
Ferrous and non-ferrous metals
Main articles:
Ferrous metallurgy
and
Non-ferrous metals
The term “ferrous” is derived from the
Latin
word meaning “containing iron”. This can include pure iron, such as
wrought iron
, or an alloy such as steel. Ferrous metals are often magnetic, but not exclusively. Non-ferrous metals—alloys—lack appreciable amounts of iron.
Brittle metal
While nearly all metals are malleable or ductile, a few—beryllium, chromium, manganese, gallium, and bismuth—are brittle.
[7]
Arsenic, and antimony, if admitted as metals, are brittle. Low values of the ratio of bulk
elastic modulus
to
shear modulus
(
Pugh’s criterion
) are indicative of intrinsic brittleness.
Refractory metal
Main article:
Refractory metal
In materials science, metallurgy, and engineering, a refractory metal is a metal that is extraordinarily resistant to heat and wear. Which metals belong to this category varies; the most common definition includes niobium, molybdenum, tantalum, tungsten, and rhenium. They all have melting points above 2000 °C, and a high
hardness
at room temperature.
·
Niobium crystals, and a 1 cm3
anodized
niobium cube for comparison
·
Molybdenum crystals, and a 1 cm3 molybdenum cube for comparison
·
Tantalum single crystal, some crystalline fragments, and a 1 cm3 tantalum cube for comparison
·
Tungsten rods with evaporated crystals, partially
oxidized
with colorful tarnish, and a 1 cm3 tungsten cube for comparison
·
Rhenium single crystal, a remelted bar, and a 1 cm3 rhenium cube for comparison
White metal
A
white metal
is any of range of white-coloured metals (or their alloys) with relatively low melting points. Such metals include zinc, cadmium, tin, antimony (here counted as a metal), lead, and bismuth, some of which are quite toxic. In Britain, the fine art trade uses the term “white metal” in auction catalogues to describe foreign silver items which do not carry British Assay Office marks, but which are nonetheless understood to be silver and are priced accordingly.
Heavy and light metals
Main articles:
Heavy metals
and
Light metals
A
heavy metal
is any relatively dense metal or metalloid.
[8]
More specific definitions have been proposed, but none have obtained widespread acceptance. Some heavy metals have niche uses, or are notably toxic; some are essential in trace amounts. All other metals are light metals.
Base, noble and precious metals
Main articles:
Base metal
,
noble metal
, and
precious metal
In chemistry, the term base metal is used informally to refer to a metal that is easily oxidized or
corroded
, such as reacting easily with dilute
hydrochloric acid
(HCl) to form a metal chloride and hydrogen. Examples include iron, nickel, lead and zinc. Copper is considered a base metal as it is oxidized relatively easily, although it does not react with HCl.
Rhodium
, a noble metal, shown here as 1 g of powder, a 1 g pressed cylinder, and a 1 g pellet.
The term noble metal is commonly used in opposition to base metal. Noble metals are resistant to corrosion or oxidation,
[9]
unlike most
base metals
. They tend to be precious metals, often due to perceived rarity. Examples include gold, platinum, silver, rhodium, iridium and palladium.
In
alchemy
and
numismatics
, the term base metal is contrasted with precious metal, that is, those of high economic value.
[10]
A longtime goal of the
alchemists
was the transmutation of base metals into precious metals including such coinage metals as silver and gold. Most coins today are made of base metals with
no intrinsic value
, in the past, coins frequently derived their value primarily from their precious metal content.
Chemically, the precious metals (like the noble metals) are less reactive than most elements, have high luster and high electrical conductivity. Historically, precious metals were important as
currency
, but are now regarded mainly as investment and industrial
commodities
. Gold, silver, platinum and palladium each have an
ISO 4217
currency code. The best-known precious metals are gold and silver. While both have industrial uses, they are better known for their uses in art,
jewelry
, and coinage. Other precious metals include the
platinum group
metals: ruthenium, rhodium, palladium, osmium, iridium, and platinum, of which platinum is the most widely traded.
The demand for precious metals is driven not only by their practical use, but also by their role as investments and a
store of value
.
[11]
Palladium and platinum, as of fall 2018, were valued at about three quarters the price of gold. Silver is substantially less expensive than these metals, but is often traditionally considered a precious metal in light of its role in coinage and jewelry.
Lifecycle
Formation
See also:
Nucleosynthesis
Metals in the Earth’s crust: · v |
|
abundance and main occurrence or source, by weight |
|
14 |
|
I |
|
Most abundant (up to 82000 ppm) |
|
Abundant (100–999 ppm) |
|
Uncommon (1–99 ppm) |
|
Rare (0.01–0.99 ppm) |
|
Very rare (0.0001–0.0099 ppm) |
|
Metals left of the dividing line occur (or are sourced) mainly as lithophiles; those to the right, as chalcophiles except gold (a siderophile) and tin (a lithophile). |
This sub-section deals with the formation of periodic table elemental metals since these form the basis of metallic materials, as defined in this article.
Metals up to the
vicinity of iron
(in the periodic table) are largely made via
stellar nucleosynthesis
. In this process, lighter elements from hydrogen to silicon undergo successive
fusion
reactions inside stars, releasing light and heat and forming heavier elements with higher
atomic numbers
.
[12]
Heavier metals are not usually formed this way since fusion reactions involving such nuclei would consume rather than release energy.
[13]
Rather, they are largely synthesised (from elements with a lower atomic number) by
neutron capture
, with the two main modes of this repetitive capture being the
s-process
and the
r-process
. In the s-process (“s” stands for “slow”), singular captures are separated by years or decades, allowing the less stable nuclei to
beta decay
,
[14]
while in the r-process (“rapid”), captures happen faster than nuclei can decay. Therefore, the s-process takes a more or less clear path: for example, stable cadmium-110 nuclei are successively bombarded by free neutrons inside a star until they form cadmium-115 nuclei which are unstable and decay to form indium-115 (which is nearly stable, with a half-life 30000 times the age of the universe). These nuclei capture neutrons and form indium-116, which is unstable, and decays to form tin-116, and so on.[12]
[15]
[n 3]
In contrast, there is no such path in the r-process. The s-process stops at bismuth due to the short half-lives of the next two elements, polonium and astatine, which decay to bismuth or lead. The r-process is so fast it can skip this zone of instability and go on to create heavier elements such as thorium and uranium.
[17]
Metals condense in planets as a result of stellar evolution and destruction processes. Stars lose much of their mass when it is
ejected
late in their lifetimes, and sometimes thereafter as a result of a
neutron star
merger,
[18]
[n 4]
thereby increasing the abundance of elements heavier than helium in the
interstellar medium
. When gravitational attraction causes this matter to coalesce and collapse
new stars and planets are formed
.
[20]
Abundance and occurrence
See also:
Abundance of the chemical elements
A sample of
diaspore
, an aluminium oxide hydroxide mineral, α-AlO(OH)
The Earth’s crust is made of approximately 25% of metals by weight, of which 80% are light metals such as sodium, magnesium, and aluminium. Nonmetals (~75%) make up the rest of the crust. Despite the overall scarcity of some heavier metals such as copper, they can become concentrated in economically extractable quantities as a result of mountain building, erosion, or other geological processes.
Metals are primarily found as lithophiles (rock-loving) or chalcophiles (ore-loving). Lithophile metals are mainly the s-block elements, the more reactive of the d-block elements. and the f-block elements. They have a strong affinity for oxygen and mostly exist as relatively low density silicate minerals. Chalcophile metals are mainly the less reactive d-block elements, and the period 4–6 p-block metals. They are usually found in (insoluble) sulfide minerals. Being denser than the lithophiles, hence sinking lower into the crust at the time of its solidification, the chalcophiles tend to be less abundant than the lithophiles.
On the other hand, gold is a siderophile, or iron-loving element. It does not readily form compounds with either oxygen or sulfur. At the time of the Earth’s formation, and as the most noble (inert) of metals, gold sank into the core due to its tendency to form high-density metallic alloys. Consequently, it is a relatively rare metal. Some other (less) noble metals—molybdenum, rhenium, the platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, and platinum), germanium, and tin—can be counted as siderophiles but only in terms of their primary occurrence in the Earth (core, mantle and crust), rather the crust. These metals otherwise occur in the crust, in small quantities, chiefly as chalcophiles (less so in their native form).
[n 5]
The rotating fluid outer core of the Earth’s interior, which is composed mostly of iron, is thought to be the source of Earth’s protective magnetic field.
[n 6]
The core lies above Earth’s solid inner core and below its mantle. If it could be rearranged into a column having a 5 m2 (54 sq ft) footprint it would have a height of nearly 700 light years. The magnetic field shields the Earth from the charged particles of the solar wind, and cosmic rays that would otherwise strip away the upper atmosphere (including the ozone layer that limits the transmission of ultraviolet radiation).
Extraction
Main articles:
Ore
,
Mining
, and
Extractive metallurgy
Metals are often extracted from the Earth by means of
mining
ores that are rich sources of the requisite elements, such as
bauxite
. Ore is located by
prospecting
techniques, followed by the exploration and examination of deposits. Mineral sources are generally divided into
surface mines
, which are mined by excavation using heavy equipment, and
subsurface mines
. In some cases, the sale price of the metal/s involved make it economically feasible to mine lower concentration sources.
Once the ore is mined, the metals must be extracted, usually by chemical or electrolytic reduction.
Pyrometallurgy
uses high temperatures to convert ore into raw metals, while
hydrometallurgy
employs
aqueous
chemistry for the same purpose. The methods used depend on the metal and their contaminants.
When a metal ore is an ionic compound of that metal and a non-metal, the ore must usually be
smelted
—heated with a reducing agent—to extract the pure metal. Many common metals, such as iron, are smelted using carbon as a reducing agent. Some metals, such as aluminium and sodium, have no commercially practical reducing agent, and are extracted using
electrolysis
instead.
[21]
[22]
Sulfide
ores are not reduced directly to the metal but are roasted in air to convert them to oxides.
Uses
A neodymium compound alloy magnet of composition Nd2Fe14B on a
nickel-iron
bracket from a computer
hard drive
Metals are present in nearly all aspects of modern life. Iron, a heavy metal, may be the most common as it accounts for 90% of all refined metals; aluminium, a light metal, is the next most commonly refined metal. Pure iron may be the cheapest metallic element of all at cost of about US$0.07 per gram. Its ores are widespread; it is easy to refine; and the technology involved has been developed over hundreds of years.
Cast iron
is even cheaper, at a fraction of US$0.01 per gram, because there is no need for subsequent purification. Platinum, at a cost of about $27 per gram, may be the most ubiquitous given its very high melting point, resistance to corrosion, electrical conductivity, and durability. It is said to be found in, or used to produce, 20% of all consumer goods. Polonium is likely to be the most expensive metal, at a notional cost of about $100,000,000 per gram,[
citation needed
] due to its scarcity and micro-scale production.
Some metals and metal alloys possess high structural strength per unit mass, making them useful materials for carrying large loads or resisting impact damage. Metal alloys can be engineered to have high resistance to shear, torque and deformation. However the same metal can also be vulnerable to fatigue damage through repeated use or from sudden stress failure when a load capacity is exceeded. The strength and resilience of metals has led to their frequent use in high-rise building and bridge construction, as well as most vehicles, many appliances, tools, pipes, and railroad tracks.
Metals are good conductors, making them valuable in electrical appliances and for carrying an electric current over a distance with little energy lost. Electrical power grids rely on metal cables to distribute electricity. Home electrical systems, for the most part, are wired with copper wire for its good conducting properties.
The thermal conductivity of metals is useful for containers to heat materials over a flame. Metals are also used for
heat sinks
to protect sensitive equipment from overheating.
The high reflectivity of some metals enables their use in mirrors, including precision astronomical instruments, and adds to the aesthetics of metallic jewelry.
Some metals have specialized uses; mercury is a liquid at room temperature and is used in switches to complete a circuit when it flows over the switch contacts. Radioactive metals such as uranium and plutonium are used in
nuclear power plants
to produce energy via
nuclear fission
.
Shape memory alloys
are used for applications such as pipes, fasteners and vascular
stents
.
Metals can be
doped
with foreign molecules—organic, inorganic, biological and polymers. This doping entails the metal with new properties that are induced by the guest molecules. Applications in catalysis, medicine, electrochemical cells, corrosion and more have been developed.
[23]
Recycling
A pile of compacted steel scraps, ready for recycling
Demand for metals is closely linked to economic growth given their use in
infrastructure
, construction, manufacturing, and consumer goods. During the 20th century, the variety of metals used in society grew rapidly. Today, the development of major nations, such as China and India, and technological advances, are fuelling ever more demand. The result is that mining activities are expanding, and more and more of the world’s metal stocks are above ground in use, rather than below ground as unused reserves. An example is the in-use stock of copper. Between 1932 and 1999, copper in use in the U.S. rose from 73 g to 238 g per person.
[24]
Metals are inherently recyclable, so in principle, can be used over and over again, minimizing these negative environmental impacts and saving energy. For example, 95% of the energy used to make aluminium from bauxite ore is saved by using recycled material.
[25]
Globally, metal recycling is generally low. In 2010, the
International Resource Panel
, hosted by the
United Nations Environment Programme
published reports on metal stocks that exist within society
[26]
and their recycling rates.[24] The authors of the report observed that the metal stocks in society can serve as huge mines above ground. They warned that the recycling rates of some rare metals used in applications such as mobile phones, battery packs for hybrid cars and fuel cells are so low that unless future end-of-life recycling rates are dramatically stepped up these critical metals will become unavailable for use in modern technology.
Biological interactions
See also:
Mineral (nutrient)
;
Metal toxicity
Some metals are either essential nutrients (typically iron, cobalt, and zinc), or relatively harmless (such as ruthenium, silver, and indium), but can be toxic in larger amounts or certain forms. Other metals, such as cadmium, mercury, and lead, are highly poisonous. Potential sources of metal poisoning include mining,
tailings
,
industrial wastes
,
agricultural runoff
,
occupational exposure
,
paints
and
treated timber
.
History
Prehistory
Copper, which occurs in native form, may have been the first metal discovered given its distinctive appearance, heaviness, and malleability compared to other stones or pebbles. Gold, silver, and iron (as meteoric iron), and lead were likewise discovered in prehistory. Forms of brass, an alloy of copper and zinc made by concurrently smelting the ores of these metals, originate from this period (although pure zinc was not isolated until the 13th century). The malleability of the solid metals led to the first attempts to craft metal ornaments, tools, and
weapons
. Meteoric iron containing nickel was discovered from time to time and, in some respects this was superior to any industrial steel manufactured up to the 1880s when alloy steels become prominent.[
citation needed
]
·
Native copper
·
Gold crystals
·
Crystalline silver
·
A slice of meteoric iron
·
Oxidised
lead
nodules and 1 cm3 cube
·
A brass weight (35 g)
Antiquity
The
Artemision Bronze
[n 7]
showing either
Poseidon
or
Zeus
, c. 460 BCE,
National Archaeological Museum
,
Athens
. The figure is more than 2 m in height.
The discovery of bronze (an alloy of copper with arsenic or tin) enabled people to create metal objects which were harder and more durable than previously possible. Bronze tools, weapons, armor, and
building materials
such as decorative tiles were harder and more durable than their stone and copper (“
Chalcolithic
“) predecessors. Initially, bronze was made of copper and arsenic (forming
arsenic bronze
) by smelting naturally or artificially mixed ores of copper and arsenic.
[27]
The earliest
artifacts
so far known come from the
Iranian plateau
in the 5th millennium BCE.
[28]
It was only later that tin was used, becoming the major non-copper ingredient of bronze in the late 3rd millennium BCE.[29] Pure tin itself was first isolated in 1800 BCE by Chinese and Japanese metalworkers.
Mercury was known to ancient Chinese and Indians before 2000 BCE, and found in Egyptian tombs dating from 1500 BCE.
The earliest known production of steel, an iron-carbon alloy, is seen in pieces of ironware excavated from an
archaeological site
in
Anatolia
(
Kaman-Kalehöyük
) and are nearly 4,000 years old, dating from 1800 BCE.
[30]
[31]
From about 500 BCE sword-makers of
Toledo, Spain
were making early forms of alloy steel by adding a mineral called
wolframite
, which contained tungsten and manganese, to iron ore (and carbon). The resulting
Toledo steel
came to the attention of Rome when used by Hannibal in the
Punic Wars
. It soon became the basis for the weaponry of Roman legions; their swords were said to have been “so keen that there is no helmet which cannot be cut through by them.”[
citation needed
]
[n 8]
In pre-Columbian America
, objects made of
tumbaga
, an alloy of copper and gold, started being produced in Panama and Costa Rica between 300–500 CE. Small metal sculptures were common and an extensive range of tumbaga (and gold) ornaments comprised the usual regalia of persons of high status.
At around the same time indigenous Ecuadorians were combining gold with a naturally-occurring platinum alloy containing small amounts of palladium, rhodium, and iridium, to produce miniatures and masks composed of a white gold-platinum alloy. The metal workers involved heated gold with
grains
of the platinum alloy until the gold melted at which point the platinum group metals became bound within the gold. After cooling, the resulting conglomeration was hammered and reheated repeatedly until it became as homogenous as if all of the metals concerned had been melted together (attaining the melting points of the platinum group metals concerned was beyond the technology of the day).
[32]
[n 9]
·
A droplet of solidified molten tin
·
Mercury being
poured into a
petri dish
·
Electrum, a natural alloy of silver and gold, was often used for making coins. Shown is the Roman god Apollo, and on the obverse, a Delphi tripod (circa 310–305 BCE).
·
A plate made of
pewter
, an alloy of 85–99% tin and (usually) copper. Pewter was first used around the beginning of the Bronze Age in the Near East.
·
A pectoral (ornamental breastplate) made of tumbaga, an alloy of gold and copper
Middle Ages
Gold is for the mistress—silver for the maid—
Copper for the craftsman cunning at his trade.
“Good!” said the Baron, sitting in his hall,
“But Iron—
Cold Iron
—is master of them all.”
from Cold Iron by
Rudyard Kipling
[33]
Arabic and medieval alchemists believed that all metals and matter were composed of the principle of sulfur, the father of all metals and carrying the combustible property, and the principle of mercury, the mother of all metals
[n 10]
and carrier of the liquidity, fusibility, and volatility properties. These principles were not necessarily the common substances sulfur and mercury found in most laboratories. This theory reinforced the belief that all metals were destined to become gold in the bowels of the earth through the proper combinations of heat, digestion, time, and elimination of contaminants, all of which could be developed and hastened through the knowledge and methods of alchemy.
[n 11]
Arsenic, zinc, antimony, and bismuth became known, although these were at first called semimetals or bastard metals on account of their immalleability. All four may have been used incidentally in earlier times without recognising their nature.
Albertus Magnus
is believed to have been the first to isolate arsenic from a compound in 1250, by heating soap together with
arsenic trisulfide
. Metallic zinc, which is brittle if impure, was isolated in India by 1300 AD. The first description of a procedure for isolating antimony is in the 1540 book
De la pirotechnia
by
Vannoccio Biringuccio
. Bismuth was described by Agricola in
De Natura Fossilium
(c. 1546); it had been confused in early times with tin and lead because of its resemblance to those elements.
·
Arsenic, sealed in a container to prevent tarnishing
·
Zinc fragments and a 1 cm3 cube
·
Antimony, showing its brilliant lustre
·
Bismuth in crystalline form, with a very thin oxidation layer, and a 1 cm3 bismuth cube
The Renaissance
De re metallica
, 1555
Platinum crystals
A disc of highly enriched uranium that was recovered from scrap processed at the
Y-12 National Security Complex
, in
Oak Ridge, Tennessee
Ultrapure cerium under argon, 1.5 gm
The first systematic text on the arts of mining and metallurgy was
De la Pirotechnia
(1540) by Vannoccio Biringuccio, which treats the examination, fusion, and working of metals.
Sixteen years later,
Georgius Agricola
published
De Re Metallica
in 1556, a clear and complete account of the profession of mining, metallurgy, and the accessory arts and sciences, as well as qualifying as the greatest treatise on the chemical industry through the sixteenth century.
He gave the following description of a metal in his
De Natura Fossilium
(1546):
Metal is a mineral body, by nature either liquid or somewhat hard. The latter may be melted by the heat of the fire, but when it has cooled down again and lost all heat, it becomes hard again and resumes its proper form. In this respect it differs from the stone which melts in the fire, for although the latter regain its hardness, yet it loses its pristine form and properties.
Traditionally there are six different kinds of metals, namely gold, silver, copper, iron, tin and lead. There are really others, for
quicksilver
is a metal, although the Alchemists disagree with us on this subject, and bismuth is also. The ancient Greek writers seem to have been ignorant of bismuth, wherefore Ammonius rightly states that there are many species of metals, animals, and plants which are unknown to us.
Stibium
when smelted in the crucible and refined has as much right to be regarded as a proper metal as is accorded to lead by writers. If when smelted, a certain portion be added to tin, a bookseller’s alloy is produced from which the type is made that is used by those who print books on paper.
Each metal has its own form which it preserves when separated from those metals which were mixed with it. Therefore neither
electrum
nor Stannum [not meaning our tin] is of itself a real metal, but rather an alloy of two metals. Electrum is an alloy of gold and silver, Stannum of lead and silver. And yet if silver be parted from the electrum, then gold remains and not electrum; if silver be taken away from Stannum, then lead remains and not Stannum.
Whether brass, however, is found as a native metal or not, cannot be ascertained with any surety. We only know of the artificial brass, which consists of copper tinted with the colour of the mineral
calamine
. And yet if any should be dug up, it would be a proper metal. Black and white copper seem to be different from the red kind.
Metal, therefore, is by nature either solid, as I have stated, or fluid, as in the unique case of quicksilver.
But enough now concerning the simple kinds.
[34]
Platinum, the third precious metal after gold and silver, was discovered in Ecuador during the period 1736 to 1744, by the Spanish astronomer Antonio de Ulloa and his colleague the mathematician Jorge Juan y Santacilia. Ulloa was the first person to write a scientific description of the metal, in 1748.
In 1789, the German chemist Martin Heinrich Klaproth was able to isolate an oxide of uranium, which he thought was the metal itself. Klaproth was subsequently credited as the discoverer of uranium. It was not until 1841, that the French chemist Eugène-Melchior Péligot, was able to prepare the first sample of uranium metal. Henri Becquerel subsequently discovered radioactivity in 1896 by using uranium.
In the 1790s, Joseph Priestley and the Dutch chemist Martinus van Marum observed the transformative action of metal surfaces on the dehydrogenation of alcohol, a development which subsequently led, in 1831, to the industrial scale synthesis of sulphuric acid using a platinum catalyst.
In 1803, cerium was the first of the lanthanide metals to be discovered, in Bastnäs, Sweden by Jöns Jakob Berzelius and Wilhelm Hisinger, and independently by Martin Heinrich Klaproth in Germany. The lanthanide metals were largely regarded as oddities until the 1960s when methods were developed to more efficiently separate them from one another. They have subsequently found uses in cell phones, magnets, lasers, lighting, batteries, catalytic converters, and in other applications enabling modern technologies.
Other metals discovered and prepared during this time were cobalt, nickel, manganese, molybdenum, tungsten, and chromium; and some of the platinum group metals, palladium, osmium, iridium, and rhodium.
Light metals
All metals discovered until 1809 had relatively high densities; their heaviness was regarded as a singularly distinguishing criterion. From 1809 onwards, light metals such as sodium, potassium, and strontium were isolated. Their low densities challenged conventional wisdom as to the nature of metals. They behaved chemically as metals however, and were subsequently recognised as such.
Aluminium was discovered in 1824 but it was not until 1886 that an industrial large-scale production method was developed. Prices of aluminium dropped and aluminium became widely used in jewelry, everyday items, eyeglass frames, optical instruments, tableware, and foil in the 1890s and early 20th century. Aluminium’s ability to form hard yet light alloys with other metals provided the metal many uses at the time. During World War I, major governments demanded large shipments of aluminium for light strong airframes. The most common metal in use for electric power transmission today is
aluminium conductor steel reinforced
. Also seeing much use is
all-aluminum-alloy conductor
. Aluminium is used because it has about half the weight of a comparable resistance copper cable (though larger diameter due to lower
specific conductivity
), as well as being cheaper. Copper was more popular in the past and is still in use, especially at lower voltages and for grounding.
While pure metallic titanium (99.9%) was first prepared in 1910 it was not used outside the laboratory until 1932. In the 1950s and 1960s, the Soviet Union pioneered the use of titanium in military and submarine applications as part of programs related to the Cold War. Starting in the early 1950s, titanium came into use extensively in military aviation, particularly in high-performance jets, starting with aircraft such as the
F-100 Super Sabre
and
Lockheed A-12
and
SR-71
.
Metallic scandium was produced for the first time in 1937. The first pound of 99% pure scandium metal was produced in 1960. Production of aluminium-scandium alloys began in 1971 following a U.S. patent. Aluminium-scandium alloys were also developed in the USSR.
·
Sodium
·
Potassium pearls under paraffin oil. Size of the largest pearl is 0.5 cm.
·
Strontium crystals
·
Aluminium chunk,
2.6 grams, 1 x 2 cm.
·
A bar of titanium crystals
·
Scandium, including a 1 cm3 cube
The age of steel
White-hot steel pours like water from a 35-ton electric furnace, at the Allegheny Ludlum Steel Corporation, in
Brackenridge
,
Pennsylvania
The modern era in
steelmaking
began with the introduction of
Henry Bessemer
‘s
Bessemer process
in 1855, the raw material for which was pig iron. His method let him produce steel in large quantities cheaply, thus
mild steel
came to be used for most purposes for which wrought iron was formerly used. The Gilchrist-Thomas process (or basic Bessemer process) was an improvement to the Bessemer process, made by lining the converter with a basic material to remove phosphorus.
Due to its high
tensile strength
and low cost, steel came to be a major component used in
buildings
, infrastructure, tools,
ships
,
automobiles
,
machines
, appliances, and weapons.
In 1872, the Englishmen Clark and Woods patented an alloy that would today be considered a stainless steel. The corrosion resistance of iron-chromium alloys had been recognized in 1821 by French metallurgist Pierre Berthier. He noted their resistance against attack by some acids and suggested their use in cutlery. Metallurgists of the 19th century were unable to produce the combination of low carbon and high chromium found in most modern stainless steels, and the high-chromium alloys they could produce were too brittle to be practical. It was not until 1912 that the industrialisation of stainless steel alloys occurred in England, Germany, and the United States.
The last stable metallic elements
By 1900 three metals with atomic numbers less than lead (#82), the heaviest stable metal, remained to be discovered: elements 71, 72, 75.
Von Welsbach, in 1906, proved that the old ytterbium also contained a new element (#71), which he named cassiopeium. Urbain proved this simultaneously, but his samples were very impure and only contained trace quantities of the new element. Despite this, his chosen name lutetium was adopted.
In 1908, Ogawa found element 75 in thorianite but assigned it as element 43 instead of 75 and named it nipponium. In 1925 Walter Noddack, Ida Eva Tacke and Otto Berg announced its separation from gadolinite and gave it the present name, rhenium.
Georges Urbain claimed to have found element 72 in rare-earth residues, while Vladimir Vernadsky independently found it in orthite. Neither claim was confirmed due to World War I, and neither could be confirmed later, as the chemistry they reported does not match that now known for hafnium. After the war, in 1922, Coster and Hevesy found it by X-ray spectroscopic analysis in Norwegian zircon. Hafnium was thus the last stable element to be discovered.
·
Lutetium, including a 1 cm3 cube
·
Rhenium, including a 1 cm3 cube
·
Hafnium, in the form of a 1.7 kg bar
By the end of World War II scientists had synthesized four post-uranium elements, all of which are radioactive (unstable) metals: neptunium (in 1940), plutonium (1940–41), and curium and americium (1944), representing elements 93 to 96. The first two of these were eventually found in nature as well. Curium and americium were by-products of the Manhattan project, which produced the world’s first atomic bomb in 1945. The bomb was based on the nuclear fission of uranium, a metal first thought to have been discovered nearly 150 years earlier.
Post-World War II developments
Superalloys
Superalloys composed of combinations of Fe, Ni, Co, and Cr, and lesser amounts of W, Mo, Ta, Nb, Ti, and Al were developed shortly after World War II for use in high performance engines, operating at elevated temperatures (above 650 °C (1,200 °F)). They retain most of their strength under these conditions, for prolonged periods, and combine good low-temperature ductility with resistance to corrosion or oxidation. Superalloys can now be found in a wide range of applications including land, maritime, and aerospace turbines, and chemical and petroleum plants.
Transcurium metals
The successful development of the atomic bomb at the end of World War II sparked further efforts to synthesize new elements, nearly all of which are, or are expected to be, metals, and all of which are radioactive. It was not until 1949 that element 97 (berkelium), next after element 96 (curium), was synthesized by firing alpha particles at an americium target. In 1952, element 100 (fermium) was found in the debris of the first hydrogen bomb explosion; hydrogen, a nonmetal, had been identified as an element nearly 200 years earlier. Since 1952, elements 101 (mendelevium) to 117 (tennessine) have been synthesized. The most recently synthesized element is 118 (oganneson). Its status as a metal or a nonmetal—or something else—is not yet clear.
Bulk metallic glasses
A metallic glass (also known as an amorphous or glassy metal) is a solid metallic material, usually an alloy, with disordered atomic-scale structure. Most pure and alloyed metals, in their solid state, have atoms arranged in a highly ordered crystalline structure. Amorphous metals have a non-crystalline glass-like structure. But unlike common glasses, such as window glass, which are typically electrical insulators, amorphous metals have good electrical conductivity. Amorphous metals are produced in several ways, including extremely rapid cooling, physical vapor deposition, solid-state reaction, ion irradiation, and mechanical alloying. The first reported metallic glass was an alloy (Au75Si25) produced at Caltech in 1960. More recently, batches of amorphous steel with three times the strength of conventional steel alloys have been produced. Currently the most important applications rely on the special magnetic properties of some ferromagnetic metallic glasses. The low magnetization loss is used in high efficiency transformers. Theft control ID tags and other article surveillance schemes often use metallic glasses because of these magnetic properties.
Shape-memory alloys
A shape-memory alloy (SMA) is an alloy that “remembers” its original shape and when deformed returns to its pre-deformed shape when heated. While the shape memory effect had been first observed in 1932, in an Au-Cd alloy, it was not until 1962, with the accidental discovery of the effect in a Ni-Ti alloy that research began in earnest, and another ten years before commercial applications emerged. SMA’s have applications in robotics and automotive, aerospace and biomedical industries. There is another type of SMA, called a ferromagnetic shape-memory alloy (FSMA), that changes shape under strong magnetic fields. These materials are of particular interest as the magnetic response tends to be faster and more efficient than temperature-induced responses.
Quasicyrstalline alloys
A Ho-Mg-Zn icosahedral quasi
crystal form
ed as a pentagonal
dodecahedron
, the dual of the
icosahedron
.
In 1984, Israeli chemist Dan Shechtman found an aluminium-manganese alloy having five-fold symmetry, in breach of crystallographic convention at the time which said that crystalline structures could only have two-, three-, four-, or six-fold symmetry. Due to fear of the scientific community’s reaction, it took him two years to publish the results for which he was awarded the Nobel Prize in Chemistry in 2011. Since this time, hundreds of quasicrystals have been reported and confirmed. They exist in many metallic alloys (and some polymers). Quasicrystals are found most often in aluminium alloys (Al-Li-Cu, Al-Mn-Si, Al-Ni-Co, Al-Pd-Mn, Al-Cu-Fe, Al-Cu-V, etc.), but numerous other compositions are also known (Cd-Yb, Ti-Zr-Ni, Zn-Mg-Ho, Zn-Mg-Sc, In-Ag-Yb, Pd-U-Si, etc.). Quasicrystals effectively have infinitely large unit cells.
Icosahedrite
Al63Cu24Fe13, the first quasicrystal found in nature, was discovered in 2009. Most quasicrystals have ceramic-like properties including low electrical conductivity (approaching values seen in insulators) and low thermal conductivity, high hardness, brittleness, and resistance to corrosion, and non-stick properties. Quasicrystals have been used to develop heat insulation, LEDs, diesel engines, and new materials that convert heat to electricity. New applications may take advantage of the low coefficient of friction and the hardness of some quasicrystalline materials, for example embedding particles in plastic to make strong, hard-wearing, low-friction plastic gears. Other potential applications include selective solar absorbers for power conversion, broad-wavelength reflectors, and bone repair and prostheses applications where biocompatibility, low friction and corrosion resistance are required.
Complex metallic alloys
Complex metallic alloys (CMAs) are intermetallic compounds characterized by large unit cells comprising some tens up to thousands of atoms; the presence of well-defined clusters of atoms (frequently with icosahedral symmetry); and partial disorder within their crystalline lattices. They are composed of two or more metallic elements, sometimes with metalloids or
chalcogenides
added. They include, for example, NaCd2, with 348 sodium atoms and 768 cadmium atoms in the unit cell.
Linus Pauling
attempted to describe the structure of NaCd2 in 1923, but did not succeed until 1955. At first called “giant unit cell crystals”, interest in CMAs, as they came to be called, did not pick up until 2002, with the publication of a paper called “Structurally Complex Alloy Phases”, given at the 8th International Conference on Quasicrystals. Potential applications of CMAs include as heat insulation; solar heating; magnetic refrigerators; using waste heat to generate electricity; and coatings for turbine blades in military engines.
High entropy alloys
High entropy alloys (HEAs) such as AlLiMgScTi are composed of equal or nearly equal quantities of five or more metals. Compared to conventional alloys with only one or two base metals, HEAs have considerably better strength-to-weight ratios, higher tensile strength, and greater resistance to fracturing, corrosion, and oxidation. Although HEAs were described as early as 1981, significant interest did not develop until the 2010s; they continue to be the focus of research in materials science and engineering because of their potential for desirable properties.
MAX phase alloy
s
MAX phase |
|||
MAX |
M |
A |
X |
Hf2SnC |
|||
Ti4AlN3 |
|||
Ti3SiC2 |
|||
Ti2AlC |
|||
Cr2AlC2 |
|||
Ti3AlC2 |
In a MAX phase alloy, M is an early transition metal, A is an A group element (mostly group IIIA and IVA, or groups 13 and 14), and X is either carbon or nitrogen. Examples are Hf2SnC and Ti4AlN3. Such alloys have some of the best properties of metals and ceramics. These properties include high electrical and thermal conductivity, thermal shock resistance, damage tolerance, machinability, high elastic stiffness, and low thermal expansion coefficients.
[35]
They can be polished to a metallic luster because of their excellent electrical conductivities. During mechanical testing, it has been found that polycrystalline Ti3SiC2 cylinders can be repeatedly compressed at room temperature, up to stresses of 1 GPa, and fully recover upon the removal of the load. Some MAX phases are also highly resistant to chemical attack (e.g. Ti3SiC2) and high-temperature oxidation in air (Ti2AlC, Cr2AlC2, and Ti3AlC2). Potential applications for MAX phase alloys include: as tough, machinable, thermal shock-resistant refractories; high-temperature heating elements; coatings for electrical contacts; and neutron irradiation resistant parts for nuclear applications. While MAX phase alloys were discovered in the 1960s, the first paper on the subject was not published until 1996.
See also
·
Colored gold
·
Ductility
· Ferrous metallurgy
·
Metal theft
·
Metallurgy
·
Metalworking
·
Properties of metals, metalloids and nonmetals
·
Structural steel
· Transition metal
Notes
1.
^
This is a simplified explanation; other factors may include
atomic radius
,
nuclear charge
, number of bond
orbitals
, overlap of orbital energies, and crystal form.[4]
2.
^
Trace elements having an abundance equalling or much less than one part per trillion (namely Tc, Pm, Po, At, Ra, Ac, Pa, Np, and Pu) are not shown.
3.
^
In some cases, for example in the presence of
high energy gamma rays
or in a
very high temperature hydrogen rich environment
, the subject nuclei may experience neutron loss or proton gain resulting in the production of (comparatively rare)
neutron deficient isotopes
.
[16]
4.
^
The ejection of matter when two neutron stars collide is attributed to the interaction of their
tidal forces
, possible crustal disruption, and shock heating (which is what happens if you floor the accelerator in car when the engine is cold).
[19]
5.
^
Iron, cobalt, nickel, and tin are also siderophiles from a whole of Earth perspective.
6.
^
Another life-enabling role for iron is as a key constituent of
hemoglobin
, which enables the transportation of oxygen from the lungs to the rest of the body.
7.
^
Bronze is an alloy consisting primarily of copper, commonly with about 12% tin and often with the addition of other metals (such as aluminium, manganese, nickel or zinc) and sometimes non-metals or metalloids such as arsenic, phosphorus or silicon.
8.
^
The Chalybean peoples of Pontus in Asia Minor were being concurrently celebrated for working in iron and steel. Unbeknownst to them, their iron contained a high amount of manganese, enabling the production of a superior form of steel.
9.
^
In Damascus, Syria, blade-smiths were able to forge knives and swords with a distinctive surface pattern composed of swirling patterns of light-etched regions on a nearly black background. These blades had legendary cutting abilities.
The iron the smiths were using
was sourced from India, and contained one or more carbide-forming elements, such as V, Mo, Cr, Mn, and Nb. Modern analysis of these weapons has shown that these elements supported the catalytic formation of carbon nanotubes, which in turn promoted the formation of
cementite
(Fe3C) nanowires. The malleability of the carbon nanotubes offset the brittle nature of the cementite, and endowed the resulting steel with a unique combination of strength and flexibility. Knowledge of how to make what came to called
Damascus steel
died out in the eighteenth century possibly due to exhausting ore sources with the right combination of impurities. The techniques involved were not rediscovered until 2009.
10.
^
In ancient times, lead was regarded as the father of all metals.
11.
^
Paracelsus
, a later
German Renaissance
writer, added the third principle of salt, carrying the nonvolatile and incombustible properties, in his
tria prima doctrine
. These theories retained the four classical elements as underlying the composition of sulfur, mercury and salt.
References
1.
^
Yonezawa, F (2017). Physics of Metal-Nonmetal Transitions. Amsterdam: IOS Press. p. 257.
ISBN
978-1-61499-786-3
. Sir
Nevill Mott
(1905-1996) wrote a letter to a fellow physicist,
Prof. Peter P. Edwards
, in which he notes…I’ve though a lot about ‘What is a metal?’ and I think one can only answer the question at T =0 (the absolute zero of temperature). There a metal conducts and a nonmetal doesn’t.
2.
^
John C. Martin.
“What we learn from a star’s metal content”
. New Analysis RR Lyrae Kinematics in the Solar Neighborhood. Retrieved September 7, 2005.
3.
^
Roe, J; Roe, M (1992). “World’s coinage uses 24 chemical elements”. World Coinage News. 19 (4, 5): 24–25, 18–19.
4. ^
Jump up to:
a
b
c
d
e
Mortimer, Charles E. (1975). Chemistry: A Conceptual Approach (3rd ed.). New York: D. Van Nostrad Company.
5.
^
Ductility – strength of materials
6.
^
Holleman, A.F.; Wiberg, E. “Inorganic Chemistry” Academic Press: San Diego, 2001. ISBN
0-12-352651-5
.
7.
^
Russell, A. M; Lee, K. L. (2005). Structure–Property Relations in Nonferrous Metals. Structure-Property Relations in Nonferrous Metals. Hoboken, NJ: John Wiley & Sons. pp. passim.
Bibcode
:
2005srnm.book…..R
.
ISBN
978-0-471-64952-6
.
8.
^
Metal contamination
. Editions Quae. 2006.
ISBN
978-2-7592-0011-5
.
9.
^
Tunay, Olcay; Kabdasli, Isik; Arslan-Alaton, Idil; Olmez-Hanci, Tugba (2010).
Chemical Oxidation Applications for Industrial Wastewaters
. IWA Publishing.
ISBN
978-1-84339-307-8
.
10.
^
Walther, John V. (2013).
Earth’s Natural Resources
. Jones & Bartlett Publishers.
ISBN
978-1-4496-3234-2
.
11.
^
Abdul-Rahman, Yahia (2014).
The Art of RF (Riba-Free) Islamic Banking and Finance:
Tools
and Techniques for Community-Based Banking
. John Wiley & Sons.
ISBN
978-1-118-77096-2
.
12. ^ Jump up to:
a
b
Cox 1997
, pp. 73–89
13.
^
Cox 1997, pp. 32, 63, 85
14.
^
Podosek 2011
, p. 482
15.
^
Padmanabhan 2001
, p. 234
16.
^
Rehder 2010
, pp. 32, 33
17.
^
Hofmann 2002
, pp. 23–24
18.
^
Hadhazy 2016
19.
^
Choptuik, Lehner & Pretorias 2015
, p. 383
20.
^
Cox 1997, pp. 83, 91, 102–103
21.
^
“Los Alamos National Laboratory – Sodium”
. Retrieved 2007-06-08.
22.
^
“Los Alamos National Laboratory – Aluminum”
. Retrieved 2007-06-08.
23.
^
Avnir, David (2014). “Molecularly doped metals”. Acc. Chem. Res. 47 (2): 579–592.
doi
:
10.1021/ar4001982
.
PMID
24283194
.
24. ^ Jump up to:
a
b
The Recycling Rates of Metals: A Status Report
Archived
2016-01-01 at the
Wayback Machine
2010, International Resource Panel, United Nations Environment Programme
25.
^
Tread lightly: Aluminium attack
Carolyn Fry, Guardian.co.uk, 22 February 2008.
26.
^
Metal Stocks in Society: Scientific Synthesis
Archived 2016-01-01 at the Wayback Machine 2010, International Resource Panel, United Nations Environment Programme
27.
^
Tylecote, R.F. (1992).
A History of Metallurgy, Second Edition
. London: Maney Publishing, for the Institute of Materials.
ISBN
978-1-902653-79-2
. Archived from
the original
on 2015-04-02.
28.
^
Thornton, C.; Lamberg-Karlovsky, C.C.; Liezers, M.; Young, S.M.M. (2002). “On pins and needles: tracing the evolution of copper-based alloying at Tepe Yahya, Iran, via ICP-MS analysis of Common-place items”. Journal of Archaeological Science. 29(12): 1451–1460.
doi
:
10.1006/jasc.2002.0809
.
29.
^
Kaufman, Brett. “Metallurgy and Archaeological Change in the Ancient Near East”. Backdirt: Annual Review. 2011: 86.
30.
^
Akanuma, H. (2005). “The significance of the composition of excavated iron fragments taken from Stratum III at the site of Kaman-Kalehöyük, Turkey”. Anatolian Archaeological Studies. Tokyo: Japanese Institute of Anatolian Archaeology. 14: 147–158.
31.
^
“Ironware piece unearthed from Turkey found to be oldest steel”
. The Hindu. Chennai, India. 2009-03-26. Archived from
the original
on 2009-03-29. Retrieved 2009-03-27.
32.
^
Knauth, P (1976). The Metalsmiths, revised edition. London: Time-Life International. pp. 133, 137.
33.
^
Published in
The Delineator
, Sept. 1909. Reprinted as the introduction to
Rewards and Fairies
in 1910.
34.
^
Georgius Agricola,
De Re Metallica
(1556) Tr. Herbert Clark Hoover & Lou Henry Hoover (1912); Footnote quoting De Natura Fossilium (1546), p. 180
35.
^
Max phase composites
Materials Science and Engineering A
Further reading
· Crow J.M. 2016, “Impossible alloys: How to make never-before-seen metals”, New Scientist, 12 October
· Parish R.V. 1977, The Metallic Elements, Longman, London, ISBN
978-0-582-44278-8
· Raymond R. 1984, Out of the Fiery Furnace: The Impact of Metals on the History of Mankind, Macmillan Australia, Melbourne, ISBN
978-0-333-38024-6
· Russell A.M. & Lee K L. 2005, Structure–Property Relations in Nonferrous Metals, John Wiley & Sons, Hoboken, New Jersey, ISBN 978-0-471-64952-6
· Street A. & Alexander W. 1998, Metals in the Service of Man (11th ed.), Penguin Books, London, ISBN
978-0-14-025776-2
· Wilson A.J. 1994, The Living Rock: The Story of Metals Since Earliest Times and Their Impact on Developing Civilization, Woodhead Publishing, Cambridge, ISBN
978-1-85573-154-7
External links
Wikisource has the text of the 1879 |
·
ASM International
(formerly the American Society for Metals)
·
Strong as Titanium, Cheap as Dirt: New Steel Alloy Shines
·
The Minerals, Metals & Materials Society Home Page
show · v · t · e Periodic table |
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hide · v · t · e
Periodic table |
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Pm |
Ra |
Ac |
Np |
Pu |
Alkali metal Alkaline earth metal Lanthanide Actinide Transition metal Post-transition metal Metalloid Reactive nonmetal Noble gas Unknown |
Authority control |
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CHEM 102: LECTURE 3 The Chemical Revolution of Lavoisier
Lavoisier’s Laboratory, Musée des Arts et Métiers, Paris
Antoine-Laurent Lavoisier (1734 – 1794) forever changed the practice and concepts of chemistry by forging a new series of laboratory analyses that would bring order to the chaotic centuries of Greek philosophy and medieval alchemy. Lavoisier’s experimental work which led to his discovering the Law of Conservation of Mass and framing the principles of modern chemistry in his Traité élémentaire de chimie (the first Chemistry book) prompted future generations to regard him as a founder of the science.
It is generally accepted that Lavoisier’s great accomplishments in chemistry stem largely from his changing the science from a qualitative to a quantitative one. Lavoisier is most noted for his discovery of the role oxygen plays in combustion. He recognized and named oxygen (1778) and hydrogen (1783), and opposed an earlier (phlogiston) theory of spontaneous chemical reactions. Lavoisier helped construct the metric system, wrote the first extensive list of elements and helped to reform chemical nomenclature. He predicted the existence of silicon (1787) and was also the first to establish that sulfur was an element (1777) rather than a compound. He discovered that, although matter may change its form or shape, its mass always remains the same.
The fossil fuel, natural gas (CH4), “burns” in the presence of oxygen. This is called a combustion reaction or simply oxidation.
The Law of Conservation of Mass states that Matter can neither be created or destroyed…. but it can be transformed. If you count the number of carbon atoms (black), the number of hydrogen atoms (white) and the number of oxygen atoms (red) on both sides of the chemical reaction below, they are (respectively) the same. This is made definite in the equation which follows by the integers [1 before methane (CH4), 2 before oxygen (O2), 1 before carbon dioxide (CO2) and 2 before water (H2O)].
Lavoisier’s experiments were carried out using samples of materials that could be weighed; one describes the samples as “macroscopic.” When the discussion center on atoms, the descriptor is “microscopic.” A macroscopic quantity of matter, say a glass of water, has ~ 6 x 10^23 molecules of water. Think of how big a number this is. The bill passed by
Congress to ease the economic concerns caused by coronavirus pandemic is 2 trillion dollars, which is 2 x 10^9 , 14 powers of 10 smaller!
If you had Chemistry in High School, the specification of the integers [1,2,1,2] was called “balancing the chemical equation.” What you were really being asked to do was to assume that a law deduced from experiments done on a macroscopic scale can be applied to a problem on the microscopic scale of atoms and molecules. That you were able to do so is a profound statement of the universality of a physical law of Nature.
This lecture has two objectives. The first is to review the background of ideas that led to Lavoisier’s discovery of the Law of Conservation of Mass. This journey will reveal other
Conservation Laws of Nature, statements that are valid not only at the scale of atoms and molecules, but at the scale of everyday macroscopic experiments, and to events/processes on the scale of the Universe. That is why you need to be familiar with these Laws. They apply at every length scale of the Universe, which is why they are called “universal.”
The second objective is to bring you “face to face” with Lavoisier by having you read the description “in his own words” of his discovery of the Law of Conservation of Mass, as described his seminal text, Traité élémentaire de chimie, published in 1789.
The Classical Theory of Chemistry.
1. Ideas from the Ancient World
a) Thales of Miletus (we know he lived around May 28, 585 BC)
Thales proposed that there exists ONE (“chemical”) element in Nature. Further, he proposed that that one element, the primary stuff of all things, is water.
F.Copleston, “A History of Philosophy” vol.1, part 1.
“… the phenomena of evaporation suggests that water may become mist or air,
while the phenomena of freezing might suggest that, if the process were carried
further, water could become earth. In any case, the importance of this early thinker
lies in the fact that he raised the question, what is the ultimate nature of the world;
and not in the answer that he actually gave to the question or in his reasons, be they
what they may, for giving the answer.”
b) charge [ ‘ηλεκτρον (the substance amber) = electron; ~ 600 BC ]
The ancient Greeks recognized that rubbing certain materials (friction) produced changes in that material, particularly with respect to its effect on other materials.
Today we know that charge is a characteristic of an atom or molecule which expresses either the loss or gain of electrons.
c) Democritus (468-370 BC) ; Epicurus (342-270 BC)
Democritus postulated that matter was not infinitely devisable, but that there was a limit to which it could be divided. The limiting case of minute, indivisible particles he called an atom ( άτομο ).
d) Aristotle (384-212 BC)
Apart from his foundational contributions to Philosophy, Aristotle was the first to formulate a theory of Chemistry, and to link this to an explanation of motion. In ancient Greek, his ‘kinesis’ ( κίνησις ) literally means movement or to move.
i) “Chemistry”: four elements on Earth: Earth, Air, Fire, Water ;
in the Heavens: a fifth element αἰθήρ = aether; quintessence.
ii) “Physics”: All bodies move toward their Natural Place on Earth.
For the elements Earth and Water, that place is the center of the (geocentric) universe;
the natural place of water is a concentric shell around the earth because earth is heavier;
it sinks in water.
The natural place of Air is likewise a concentric shell surrounding that of water; bubbles
rise in water.
The natural place of Fire is higher than that of air but below the innermost celestial sphere
(carrying the Moon).
2. Ideas from the Intellectual Revolution in the 17th Century
a) mass
For nearly 2000 years, people held to Aristotle’s “common sense” theory of “natural place” and motion, that a falling object had a definite “natural falling speed” proportional to its weight. Hence, in dropping two objects of different weight, the heavier object should hit the ground first.
In his inclined-plane experiment, the 26 year old Galileo found that the speed just kept increasing, and weight was irrelevant as long as friction was negligible. Both objects hit the ground at the same time. He recognized that the speed (velocity) of an object changes on falling (the concept of acceleration). This groundbreaking experiment was captured in the legend that Galileo dropped two cannonballs from the top of the Leaning Tower in his hometown of Pisa in Italy.
Check out:
Feather & Hammer Drop on Moon – YouTube
The concept of mass as a quantitative measure of inertia was introduced by Galileo (1564 – 1642) , then adopted and quantified by Newton (1642 – 1727) [ Newton was born in the year Galileo died; for historical reference, Michelangelo died in 1564, and Shakespeare was born in 1564].
Inertia is a fundamental property of all matter. It is, in effect, the resistance that a body of matter offers to a change in its speed or position upon the application of a force. The greater the mass of a body, the smaller the change produced by an applied force.
The following is what Newton proposed on the inter-relationship between mass, change in position with time (velocity, acceleration), and force.
Three Laws of Motion:
The first law states that every object will remain at rest or in uniform motion in a
straight line unless compelled to change its state by the action of an external force (F).
The second law states: Force = mass x acceleration. F = ma.
The third law states that for every action (force) in nature there is an equal and opposite
reaction.
Using these three laws (after inventing a new branch of mathematics, calculus, to solve the problem) he proved the following:
Law of Universal Gravitation;
Objects with mass feel an attractive force that is proportional to their masses and
inversely proportional to the square of the distance (R).
F = G m m’ / R^2 (G = a constant)
Importantly, this is a universal Law of Nature, applicable to processes in the nucleus, to atoms and molecules, to the macroscopic processes we study on planet Earth, to Black Holes, to events in the farthest reaches of the Universe, back to the Big Bang, a singularity in the fabric of time and space that occurred ~ 14 billion years ago. Discovery of this mind-blowing general law is one of the reasons why Newton is regarded as the greatest scientist (ever). Later in the course we will find that he also made fundamental contributions to our understanding of light, elaborated in his book
c) Conservation of Charge ( Franklin: 1706 – 1790 ; Coulomb: 1736 – 1806 )
Benjamin Franklin proposed a one-fluid theory of electricity. He imagined electricity as being a type of invisible fluid present in all matter. He posited that rubbing insulating surfaces together caused this fluid to change location, and that a flow of this fluid constitutes an electric current. He also posited that when matter contained too little of the fluid it was negatively charged, and when it had an excess it was positively charged.
Franklin laid the foundation for a very important principle: unlike charge can cancel each other, but the total amount of charge is never changed. Charge is neither created nor destroyed, although + and – charge can neutralize each other, and two kinds of charge in a neutral object can often be separated. No exceptions have ever been found.
Coulomb found experimentally that: The magnitude of the electrostatic force (F) of attraction or repulsion between two point charges (q) is directly proportional to the product of the magnitudes of charges ( q x q’ ) and inversely proportional to the square of the distance (R) between them.
F = K q q’ / R^2 (K = constant)
Notice the similarity in the mathematical structure of the Law of Universal Gravitation and Coulomb’s Law. Both involve an inverse dependence on the distance, viz., 1/R2. A product in the numerator, m x m, for Gravitation, q x q for charge interactions. Two significant differences: the constants are different and have very different values (K >>G). And, most importantly, gravitational interactions are always attractive, whereas electrical interactions can be either attractive or repulsive.
The latter point is a cardinal principle throughout Chemistry.
“Like charges repel, unlike charges attract.”
b) Conservation of Mass (Lavoisier, 1793)
So, finally, we come to Lavoisier. As a college student Lavoisier read Newton’s famous book, Philosophiæ Naturalis Principia Mathematica. Notice that it was written in Latin.
At some point, Lavoisier realized that he could begin to quantify the jungle of empirical observations about chemical reactions if he focused on the Galilean/Newtonian concept of mass.
Now, we’re off to the races!!! See below for a diagram of Lavoisier’s instruments and his description of his seminal experiment.
Above shows Lavoisier’s apparatus for studying mercury oxidation in closed environment described in his Traité Élémentaire de Chimie published in 1789
The system contained mercury (Hg)
in a resort (called a matrass) and normal air sealed by a bell jar placed in the mercury reservoir. After heating the mercury in the resort for several days, red mercury oxide (HgO)
was observed on the mercury surface.
The mercury level inside the bell jar rose up because the consumption of oxygen. When the amount of mercury oxide no longer increased, the heating was terminated and the amount of gas volume decrease was measured. Lavoisier found that the gas loss was 16% of the total volume. The mercury oxide was removed and heated again, the volume of oxygen generated was measured. It was found that the volume was the same as the 16% volume loss. The oxygen percentage (16%) was not accurate, which could be due to not all oxygen react with mercury. From this experiment, we recognize Lavoisier’s emphasis on the Conservation of Mass in his experiment design.
In Lavoisier’s own words:
I took a matrass of about 36 cubic inches, having a long neck of six or seven lines
internal diameter, and having bent the neck so as to allow of its being placed in the
furnace, in such a manner that the extremity of the neck might be inserted under a bell
glass, placed in a trough of quicksilver (mercury).
I introduced four ounces of pure mercury into the matrass and, by means of a siphon,
exhausted the air in the receiver, so as to raise the quicksilver, and I carefully marked the
height at which it stood by pasting on a slip of paper.
Having accurately noted the height of the thermometer and barometer, I lighted a
fire in the furnace, which I kept up almost continually during twelve days, so as to keep the
quicksilver almost at its boiling point.
Nothing remarkable took place during the first day: the mercury, though not boiling, was
continually evaporating and covered the interior surface of the vessel with small drops, at
first very minute, which gradually augmenting to a sufficient size, fell back into the mass
at the bottom of the vessel. On the second day, small red particles began to appear on the
surface of the mercury, which, during the four or five following days, gradually increased
in size and number, after which they ceased to increase in either respect. At the end of
twelve days seeing that the calcination (ancient word for what today is called oxidation)
of mercury did not at all increase, I extinguished the fire, and allowed the vessel to cool.
The bulk of air in the body and neck of the matrass, and in the bell glass, reduce to a
medium of 28 inches of the barometer and 10o (54.5o F) of the thermometer, at the
commencement of the experiment was about 50 cubic inches. At the end of the
experiment the remaining air, reduced to the same medium pressure and temperature,
was only between 42 and 43 cubic inches; consequently it had lost about 1/6 of its bulk.
Afterwards, having collected all the red particles formed during the experiment from
the running mercury in which the floated, I found these to amount to 45 grains.
The air which remained after the calcination of the mercury in this experiment, and which
was reduced to1/6 of its former bulk, was no longer fit either for respiration or
combustion; animals being introduced into it were suffocated in a few second, and
a taper was plunged into it, it was extinguished as if it had been immersed in water.
(In fact, he had discovered the presence of the element nitrogen).
Lavoisier then carried out the reverse experiment, heating the product (mercuric oxide)
measuring the amount of mercury that was produced and the gas (oxygen) that evolved..
Weights were taken again it was found that the weight of the reactant matched the
weight of the two products.
As for the gas that was produced,
a taper burned in it with a dazzling splendor and charcoal, instead of consuming quietly
as it does in common air, burned with a flame, attended with a decrepitating noise, like
phosphorus, and threw out such light the eyes could hardly endure it.
BALANCING EQUATIONS
The Law of Conservation of Mass, as implemented at the atomic/molecular level in balancing equations, is more than just an abstract idea. It is the bedrock of the chemical industry. Suppose, for example, you want to produce sulfuric acid (H2SO4), the substance most produced by the chemical industry World-wide. (Guess why ???)
In the first step of the production, sulfur (a solid) is oxidized to produce sulfur dioxide, SO2.
S (s) + O2(g) SO2
SO2 is then oxidized to sulfur trioxide using oxygen in the presence of a vanadium (V) oxide catalyst.
2 SO2(g) + O2(g) 2 SO3(g)
An intermediate is then formed, oleum (H2S2O7), called fuming sulfuric acid , which, dissolved in water, gives H2SO4 .
If the coefficients were ignored in the second equation, you would have no quantitative idea how much sulfuric acid would be produced in the process. Practically speaking, you would have no idea how many train loads of sulfur from Louisiana should be brought to the plant, and the “bottom line” would be a disaster. Too little sulfur or too much sulfur would wipe out the profit margin.
Below is taken from a Wikipedia website on “balancing equations.” Spending time reviewing the examples given will help understanding material later on in the course.
Balancing Equations: Practice Problems
Try your hand at balancing each of the following equations. The correct answers follow.
(a) Fe+ Cl2 → FeCl3
(b) Fe+ O2 → Fe2O3
(c) FeBr3 + H2SO4 → Fe2 (SO4 )3 + HBr
(d) C4H6O3 + H2O → C2H4O2
(e) C2H4 + O2 → CO2 + H2O
(f) C4H10O+ O2 → CO2 + H2O
(g) C7H16 + O2 → CO2 + H2O
(h) H2SiCl2 + H2O → H8Si4O4 + HCl
(i) HSiCl3 + H2O → H10Si10O15 + HCl
(j) C7H9 + HNO3 → C7H6 (NO2) 3 + H2O
(k) C5H8O2 + NaH + HCl → C5H12O2 + NaCl
Answers to Practice Problems.
(a) 2 Fe+ 3 Cl2 →2 FeCl3
(b) 4 Fe + 3 O2 → 2 Fe2O3
(c) 2 FeBr3 + 3 H2SO4 → Fe2 (SO4 )3 + 6 HBr
(d) C4H6O3 + H2O → 2 C2H4O2
(e) C2H4 + 3 O2 → 2 CO2 +2 H2O
(f) C4H10O +6 O2 →4 CO2 + 5 H2O
(g) C7H16 + 11 O2 → 7 CO2 + 8 H2O
(h) H2SiCl2 + H2O → H8Si4O4 + HCl
(i) 10 HSiCl3 + 15 H2O → H10Si10O15 + 30 HCl
(j) C7H9 + 3 HNO3 → C7H6 (NO2) 3 + 3 H2O
(k) C5H8O2 + 2 NaH + 2 HCl → C5H12O2 + 2 NaCl
CHE 1
0
2: LECTURE 2 M
e
t
als, Minerals and Money
The
I
lliad is an ancient Greek epic poem, traditionally attributed to Homer.
S
et during the Trojan War, the ten-year siege of the city of Troy (a city in Turkey, the modern-day Hisarlik) by a coalition of Greek states, it tells of battles and e
v
ents during the weeks of a quarrel between King Agamemnon and the celebrated warrior Achilles. Above is the death mask of Agamemnon, cast in GOLD, created ~ 1550–1500 B.C. and discovered in 1876 in Mycenae, Greece by Heinrich Schliemann. It has been referred to as the “Mona Lisa of Prehistory.”
Metals and minerals form some of the most beautiful crystals in nature. For example,
Go
ld as it is found in Nature
has the following structure at the
atom
ic level:
A mineral , iron pyrite, infamous in the California Gold Rush [ that began on January 24, 1848, when gold was found by James W. Marshall at Sutter’s Mill in Coloma, California ] was known as “ Fool’s Gold.” The chemical formula is Fe2S [ Iron↔Fe, Sulphur ↔ S ].
Its crystal structure is very different from that of Gold.
The
element
Sodium, Na, has the following atomic crystal structure. The structure
is termed body-centered cubic.
The ionic compound, Halite or table salt, NaCl, has the atomic structure below. Here,
the smaller gray balls are
sodium
ions, Na+, and the larger green balls are
chlorine
ions,
Cl-. Notice that the Cl- ions are larger than the Na+ ion, an important distinction which
will be explained later in the course. The structure of the mineral is octahedral.
An example of an element that forms molecular (as opposed to ionic) crystals is Carbon.
There are four “flavors” of Carbon found in Nature; these are called allotropes. The two
most common allotropes are diamond and graphite, which have very different atomic structures. Diamond has a tetrahedral structure whereas graphite has a structure like stacked sheets of chicken wire (planar sheets of hexagons).
ALLOYS
Different
metals
can form solid state mixtures of variable composition, called alloys. Alloys are analogous to liquid solutions, e.g. salt dissolved in water. There are two types of alloys, substitutional and interstitial.
When a molten metal is mixed with another substance, there are two mechanisms that can cause an alloy to form, called
atom exchange and the interstitial mechanism. The relative size of each element in the mix plays a primary role in determining which mechanism will occur. When the atoms are relatively similar in size, the atom exchange method usually happens, where some of the atoms composing the
metallic
crystals are substituted with atoms of the other constituent. This is called a substitutional alloy. Examples of substitutional alloys include BRONZE and BRASS, in which some of the copper atoms are substituted with either tin or zinc atoms respectively.
In the case of the interstitial mechanism, one atom is usually much smaller than the other and can not successfully substitute for the other type of atom in the crystals of the base metal. Instead, the smaller atoms become trapped in the spaces between the atoms of the crystal matrix, called the interstices. This is referred to as an interstitial alloy. STEEL is an example of an interstitial alloy, because the very small
carbon
atoms fit into interstices of the iron matrix.
STAINLESS STEEL is an example of a combination of interstitial and substitutional alloys, because the carbon atoms fit into the interstices, but some of the iron atoms are substituted by nickel and chromium atoms.
2. Materials in Nature:
Materials in nature can exist in three phases, as a solid, a liquid and a gas. The state
observed depends on the pressure and temperature. So, for example, water can pass
from a solid (ice), to a liquid (water) to a gas (steam) by raising the temperature.
Moreover, the temperature at which a particular “phase transition” occurs is very
specific. For water, ice forms at exactly 0o Centigrade, and gas appears at exactly
100oC. These signatures are very specific for every substance found in nature; they
are like a “fingerprint” and there are volumes in libraries and data banks with fingerprints for thousands (+) of substances.
Importantly, solids are the most ordered
state of matter
(see above), liquids
more disorganized, and
gases
are totally disorganized. Atoms in a solid are
locked in place, atoms in a liquid can break free and move around in the same
volume, and the motion of atoms in a gas is totally random, with the gas occupying
not only the original volume of the precursor liquid phase, but all the nooks and
crannies of a container.
Phase transitions, such as the ones cited above for water, occur because heat
(which is energy) is either added to or subtracted from the physical system.
A driving force for a transformation to occur is the tendency of all systems in
Nature to try to be in the most disorganized state possible. This tendency
to become disorganized (or more random) is characterized by the increase
in a property called the entropy.
The drive, or perhaps better the drift, of any system in Nature to reach a stable
state is therefore a consequence of two factors. One is the tendency toward the
most stable, lowest energy state. The other is the tendency toward maximum
disorder (maximum entropy)
These two observations have been canonized in by two , fundamental generalizations,
called Conservation Laws. Textbook statements of these two laws follow:
First Law of Thermodynamics
The Law of Conservation of Energy states that the total
energy
of an
isolated system
is constant; energy can be transformed from one form to another, but can be neither created nor destroyed.
Second Law of Thermodynamics
This law states that the total
entropy
of an
isolated system
can never decrease over time. The total entropy can remain constant in ideal cases where the system is in a steady state (
equilibrium
), or is undergoing a
reversible process
. In all
spontaneous processes
, the total entropy increases and the process is
irreversible
. The increase in entropy accounts for the irreversibility of natural processes, and the
asymmetry between future and past
time.
3. The
Periodic Table
Over the course of centuries, and particularly in the late Middle Ages, new substances were discovered (for example, phosphorus) that expanded the list of elements known since antiquity.
With the publication in 1800 of
V
olta’s discovery of the battery, a plethora of new
elements and new perspectives were discovered/reported. These led, eventually,
to the publication in 1869 of Mendeleev’s “periodic table” which is the single
most important organizing principle in Chemistry.
The periodic table of elements is organized so that one can quickly discern the properties of individual elements such as their mass,
electron
number,
electron configuration
and their unique
chemical properties
. Metals reside on the left side of the table, while non-metals reside on the right.
The foundational study on the periodicity of properties of elements was reported by the Russian chemist Mendeleev (1834 – 1907). He used the Periodic Law not only to correct the then-accepted properties of some known elements, such as the valence and atomic weight of uranium, but also to predict the properties of eight elements that were yet to be discovered. His original Periodic Table, reported in 1869, follows.
The modern version is below.
At the end of this file I have reproduced the Wikipedia website on the Periodic Table.
It is worth spending time on this website, as it will be useful throughout the course.
4. Why GOLD ???
From the desk mask of Tutankhamun (below) to that of Agamemnon (see top of file),
from jewelry
[ A Moche gold necklace depicting feline heads. Larco Museum Collection, Lima, Peru ]
to the representation of religious or cultural themes [See below the Musica raft, ~600-1600 AD. The figure refers to the ceremony of the legend of El Dorado. The
zipa
used to cover his body in gold dust, and from his raft, he offered treasures to the
Guatavita
goddess in the middle of the sacred lake. This old Muisca tradition became the origin of the legend of El Dorado. On display in the Gold Museum in Bogota, Columbia.]
to money,
[ Gold coin of Eucraides I (171–145 BC), one of the Hellenistic rulers of ancient Ai-Khanoum. This is the largest known gold coin minted in antiquity (169,20 g; 58 mm) ]
GOLD has been a benchmark of wealth for the World’s civilizations.
[ An Indian tribute-bearer at Apadana, from the Achaemenid satrapy of Hindush, carrying gold on a yoke, circa 500 BC. ]
Gold can stimulate a subjective personal experience, but gold can also be objectified if it’s adopted as a system of exchange. This duplicity is a conundrum that is unique to gold as a commodity. Gold can be something quantitative and tangible, like money, and at the same time, it can embody something ephemeral, like a feeling, even a host of feelings. So, part of the reason that gold has always had value lies in the psychology and nature of the human experience.
But, why?
Well, for openers it never changes its appearance. The death mask of Agamemnon looks
the same today as the day it was cast. Chemically, this is a profound attribute not shared
by any other element to the same degree. For example, Silver is a beautiful metal, but can
tarnish. Gold is inert chemically to gases/liquids/solids in its environment.
Secondly, it is the most malleable of elements. Physically, this is an attribute unmatched by any other element. A gold nugget of 0.5 cm (0.20 in) in size can be hammered into a gold foil of about 0.5 m2 (5.4 sq ft). It is this property which accounts for the use of Gold since antiquity for jewelry and the beautiful objects created by gifted craftsmen.
The central role of Gold in our monetary system is more problematical. Hunter Gatherer societies functioned without money. Such societies were characterized by Thomas Hobbes [ English philosopher and political theorist best known for his book “Leviathan” (1651) ], as “solitary, poor, nasty, brutish and short.”
But, it is important to note that sophisticated societies have also functioned without money.
Five hundred years ago, the most sophisticated society in South America, the Inca Empire, was moneyless.
Labor was the unit of value in the Inca Empire, just as it was supposed to be in a
Communist society. Recall Karl Marx (1818-1883), who sought to demonstrate in
“Das Kaptial,” that money is commoditized labor the surplus generated by honest toil, appropriated and ‘reified’ in order to satisfy the capitalist class’s insatiable lust for accumulation.
If, however, one adopts a substance (say, an element) as the basis of a monetary system, what are the chemical and physical properties that are desirable? Sanat Kumar [Chair of the Department of Chemical Engineering at Columbia University] has provided insight. He focuses on four qualities that an element must meet to stand alone as a currency.
First, it can’t be a gas — gases simply are not practical for currency exchange. That knocks out a bunch of contenders from the right side of the periodic table, including the
Noble gases
, which would meet the other three qualifications.
Second, it can’t be corrosive or
reactive
— pure lithium (Li), for example, ignites when exposed to water or air. Iron (Fe) rusts. This qualification knocks out 38 elements.
Third, it can’t be radioactive. For one thing, your money would eventually radiate away to nothing. For another, the radiation would eventually kill you. This eliminates the two rows that are separate from table, the elements known as
actinides
and
lanthanides
.
Any of the 30 or so remaining elements would make nice, stable forms of currency if they met the fourth qualification: They must be rare enough to be valuable, but not so rare that it’s impossible to find them.
That brings us to five elements: rhodium (Rh), palladium (Pd) ,
platinum
(Pt), silver (Ag) and gold (Au).
Although silver has been used for currency, it tarnishes easily, so it’s out. Rhodium and Palladium were discovered only in the 1800s, so they’d have been of no use to early civilizations. That leaves Gold and Platinum. Platinum, however, has a melting point around 3,000 degrees Fahrenheit (about 1,600 degrees Celsius), which could only be attained in a modern furnace, so early civilizations would not have been able to conveniently shape it into uniform units.
That leaves Gold, which is solid but malleable, doesn’t react, and won’t kill you.
So what does this process of elemental elimination tell us about what makes a good currency?
A currency needs to be stable, portable and non-toxic. And it needs to be fairly rare – you might be surprised just how little gold there is in the world.
If you were to collect together every earring, every gold sovereign, the tiny traces gold in every computer chip, every pre-Columbian statuette, every wedding ring and melt it down, it’s guesstimated that you’d be left with approximately one volume of (20 meter)^3 . In English units, 20 meters = 21.87 yards. Think of the “20 yard line” on a football field;
a volume ~20 yards on each of three sides is the estimate given.
But scarcity and stability aren’t the whole story. Gold has one other quality that makes it the stand-out contender for currency in the periodic table. Gold is… golden.
All the other metals in the periodic table are silvery-colored except for copper.
BUT copper corrodes, turning green when exposed to moist air. That makes gold very distinctive.
At the end of the day, that’s the secret of gold’s success as a currency. It satisfies the
advantages and attributes of “MONEY,” and it is “beautiful.”
Check out the spot value of Gold in today’s “coronavirus” environment. Gold and Palladium are the most actively traded metals in the market. In today’s Wall
Street Journal, Gold is valued at $1578.20 a troy ounce.
Periodic table
From Wikipedia, the free encyclopedia
Jump to navigation
Jump to s
earch
This article is about the table used in
chemistry
and physics. For other uses, see
Periodic table (disambiguation)
.
The periodic table, also known as the periodic table of elements, is a tabular display of the
chemical elements
, which are arranged by
atomic number
, electron configuration, and recurring chemical properties. The structure of the table
show
s
periodic trends
. The seven rows of the table, called
periods
, generally have metals on the left and
nonmetals
on the right. The columns, called
groups
, contain elements with similar chemical behaviours. Six groups have accepted names as well as assigned numbers: for example, group 17 elements are the
halogens
; and group 18 are the
noble gases
. Also displayed are four simple rectangular areas or
blocks
associated with the filling of different
atomic orbitals
.
The elements from atomic numbers 1 (
hydrogen
) through 118 (
oganesson
) have been discovered or synthesized, completing seven full rows of the periodic table.
[1]
[2]
The first 94 elements, hydrogen through
plutonium
, all occur naturally, though some are found only in trace amounts and a few were discovered in nature only after having first been synthesized.
[n 1]
Elements 95 to 118 have only been synthesized in laboratories or
nuclear reactors
.
[3]
The synthesis of elements having higher atomic numbers is currently being pursued: these elements would begin an
eighth row
, and theoretical work has been done to suggest possible candidates for this extension. Numerous synthetic
radio
isotopes
of naturally occurring elements have also been produced in laboratories.
The organization of the periodic table can be used to derive relationships between the various element properties, and also to predict chemical properties and behaviours of undiscovered or newly synthesized elements. Russian chemist
Dmitri Mendeleev
published the first recognizable periodic table in 1869, developed mainly to illustrate periodic trends of the then-known elements. He also predicted some properties of
unidentified elements
that were expected to fill gaps within the table. Most of his forecasts proved to be correct. Mendeleev’s idea has been slowly expanded and refined with the
discovery or synthesis of further new elements
and the development of new theoretical models to explain chemical behaviour. The modern periodic table now provides a useful framework for analyzing
chemical reactions
, and continues to be widely used in chemistry,
nuclear physics
and other sciences. Some discussion remains ongoing regarding the placement and categorisation of specific elements, the future extension and limits of the table, and whether there is an optimal form of the table.
Part of a series on the
Periodic table
Periodic table forms
[show]
Periodic table history
[show]
Sets of elements
By periodic table structure
[show]
By
metallic classification
[show]
By other characteristics
[show]
Elements
List of chemical elements
[show]
Properties of elements
[show]
Data pages for elements
[show]
·
Book
·
Category
·
Chemistry Portal
· v
· t
· e
Contents
·
1Overview
·
2Grouping methods
· 2.1
Groups
· 2.2
Periods
· 2.3
Blocks
· 2.4
Metals,
metalloids
and nonmetals
·
3Periodic trends and patterns
· 3.1
Electron configuration
· 3.2
Atomic radii
· 3.3
Ionization energy
· 3.4
Electronegativity
· 3.5
Electron affinity
· 3.6
Metallic character
· 3.7
Oxidation number
· 3.8
Linking or bridging groups
·
4History
· 4.1
First systemization attempts
· 4.2
Mendeleev’s table
· 4.3
Second version and further development
·
5Different periodic tables
· 5.1
The long- or 32-column table
· 5.2
Tables with different structures
·
6Open questions and
controversies
· 6.1
Placement of hydrogen and helium
· 6.2
Group 3 and its elements in periods 6 and 7
· 6.2.1
Lanthanum and
actinium
· 6.2.2
Lutetium and
lawrencium
· 6.2.3
Lanthanides and actinides
· 6.3
Groups included in the
transition metal
s
· 6.4
Elements with unknown chemical properties
· 6.5
Further periodic table extensions
· 6.6
Element with the highest possible atomic number
· 6.6.1
Bohr model
· 6.6.2
Relativistic
Dirac equation
· 6.7
Optimal form
·
7Other
·
8See also
·
9Notes
·
10References
· 10.1
Bibliography
·
11Further reading
· 12External links
Overview
· t
· e
Periodic table
Group
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Alkali metals
Alkaline earth metals
Pnictogens
Chalcogens
Halogens
Period
1
Hydrogen1H1.008
Helium2He4.0026
2
Lithium
3Li6.94
Beryllium4Be9.0122
Boron5B10.81
Carbon6C12.011
Nitrogen7N14.007
Oxygen8O15.999
Fluorine9F18.998
Neon10Ne20.180
3
Sodium11Na22.990
Magnesium12Mg24.305
Aluminium13Al26.982
Silicon14Si28.085
Phosphorus15P30.974
Sulfur16S32.06
Chlorine
17Cl35.45
Argon18Ar39.95
4
Potassium19K39.098
Calcium20Ca40.078
Scandium21Sc44.956
Titanium22Ti47.867
Vanadium23V50.942
Chromium24Cr51.996
Manganese25Mn54.938
Iron26Fe55.845
Cobalt27Co58.933
Nickel28Ni58.693
Copper29Cu63.546
Zinc30Zn65.38
Gallium31Ga69.723
Germanium32Ge72.630
Arsenic33As74.922
Selenium34Se78.971
Bromine35Br79.904
Krypton36Kr83.798
5
Rubidium37Rb85.468
Strontium38Sr87.62
Yttrium39Y88.906
Zirconium40Zr91.224
Niobium41Nb92.906
Molybdenum42Mo95.95
Technetium43Tc
[97]
Ruthenium44Ru101.07
Rhodium45Rh102.91
Palladium46Pd106.42
Silver47Ag107.87
Cadmium48Cd112.41
Indium49In114.82
Tin50Sn118.71
Antimony51Sb121.76
Tellurium52Te127.60
Iodine53I126.90
Xenon54Xe131.29
6
Caesium55Cs132.91
Barium56Ba137.33
Lanthanum57La138.91
Hafnium72Hf178.49
Tantalum73Ta180.95
Tungsten74W183.84
Rhenium75Re186.21
Osmium76Os190.23
Iridium77Ir192.22
Platinum78Pt195.08
Gol
d7
9Au196.97
Mercury80Hg200.59
Thallium81Tl204.38
Lea
d8
2Pb207.2
Bismuth83Bi208.98
Polonium84Po[209]
Astatine85At[210]
Radon
86Rn[222]
7
Francium87Fr[223]
Radium88Ra[226]
Actinium89Ac[227]
Rutherfordium104Rf[267]
Dubnium105Db[268]
Seaborg
ium106Sg[269]
Bohrium107Bh[270]
Hassium108Hs[269]
Meitnerium109Mt[278]
Darmstadtium110Ds[281]
Roentgenium111Rg[282]
Copernicium112Cn[285]
Nihonium113Nh[286]
Flerovium114Fl[289]
Moscovium115Mc[290]
Livermorium116Lv[293]
Tennessine117Ts[294]
Oganesson118Og[294]
Cerium58Ce140.12
Praseodymium59Pr140.91
Neodymium60Nd144.24
Promethium61Pm
[145]
Samarium62Sm150.36
Europium63Eu151.96
Gadolinium64Gd157.25
Terbium65Tb158.93
Dysprosium66Dy162.50
Holmium67Ho164.93
Erbium68Er167.26
Thulium69Tm168.93
Ytterbium70Yb173.05
Lutetium71Lu174.97
Thorium90Th232.04
Protactinium91Pa231.04
Uranium92U238.03
Neptunium93Np[237]
Plutonium
94Pu[244]
Americium95Am[243]
Curium96Cm[247]
Berkelium97Bk[247]
Californium98Cf[251]
Einsteinium99Es[252]
Fermium100Fm[257]
Mendelevium101Md[258]
Nobelium102No[259]
Lawrencium103Lr[266]
1 (red)=
Gas
3 (black)=
Solid
80 (green)=
Liquid
109 (gray)=Unknown Color of the atomic number shows state of matter (at
0 °C and 1 atm
)
Primordial
From
decay
Synthetic
Border shows natural occurrence of the element
Standard atomic weight
Ar, std(E)
[4]
· Ca: 40.078 — Formal short value, rounded (no uncertainty)
[5]
· Po: [209] —
mass number
of the most stable isotope
Background color shows subcategory in the metal–metalloid–nonmetal trend:
Metal |
Metalloid |
Nonmetal |
Unknown |
||||
Alkali metal |
Alkaline earth metal |
Lanthanide |
Actinide |
Transition metal |
Post-transition metal |
Reactive nonmetal |
Noble gas |
Each chemical element has a unique atomic number (Z) representing the number of
proton
s
in its
nucleus
.
[n 2]
Most elements have differing numbers of
neutrons
among different atoms, with these variants being referred to as isotopes. For example, carbon has three naturally occurring isotopes: all of its atoms have six protons and most have six neutrons as well, but about one per cent have seven neutrons, and a very small fraction have eight neutrons. Isotopes are never separated in the periodic table; they are always grouped together under a single element. Elements with no stable isotopes have the atomic masses of their most stable isotopes, where such masses are shown, listed in parentheses.
[7]
In the standard periodic table, the elements are listed in order of increasing atomic number Z (the number of protons in the nucleus of an atom). A new row (
period
) is started when a new
electron shell
has its first electron. Columns (
groups
) are determined by the electron configuration of the atom; elements with the same number of
electrons
in a particular subshell fall into the same columns (e.g.
oxygen
and
selenium
are in the same column because they both have four electrons in the outermost p-subshell). Elements with similar chemical properties generally fall into the same group in the periodic table, although in the
f-block
, and to some respect in the
d-block
, the elements in the same period tend to have similar properties, as well. Thus, it is relatively easy to predict the chemical properties of an element if one knows the properties of the elements around it.
[8]
Since 2016, the periodic table has 118 confirmed elements, from element 1 (hydrogen) to 118 (oganesson). Elements 113, 115, 117 and 118, the most recent discoveries, were officially confirmed by the
International Union of Pure and Applied Chemistry
(
IUPAC
) in December 2015. Their proposed names,
nihonium
(Nh),
moscovium
(Mc),
tennessine
(Ts) and oganesson (Og) respectively, were made official in November 2016 by IUPAC.
[9]
[10]
[11]
[12]
The first 94 elements occur naturally; the remaining 24,
americium
to oganesson (95–118), occur only when synthesized in laboratories. Of the 94 naturally occurring elements, 83 are
primordial
and 11 occur only in decay chains of primordial elements.[3] No element heavier than einsteinium (element 99) has ever been observed in macroscopic quantities in its pure form, nor has astatine (element 85);
francium
(element 87) has been only photographed in the form of light emitted from microscopic quantities (300,000 atoms).
[13]
Grouping methods
Groups
Main article:
Group (periodic table)
A group or family is a vertical column in the periodic table. Groups usually have more significant periodic trends than periods and blocks, explained below. Modern
quantum mechanical
theories of atomic structure explain group trends by proposing that elements within the same group generally have the same electron configurations in their
valence shell
.
[14]
Consequently, elements in the same group tend to have a shared chemistry and exhibit a clear trend in properties with increasing atomic number.
[15]
In some parts of the periodic table, such as the d-block and the f-block, horizontal similarities can be as important as, or more pronounced than, vertical similarities.
[16]
[17]
[18]
Under an international naming convention, the groups are numbered numerically from 1 to 18 from the leftmost column (the
alkali metals
) to the rightmost column (the noble gases).
[19]
Previously, they were known by
roman numerals
. In America, the roman numerals were followed by either an “A” if the group was in the
s-
or
p-block
, or a “B” if the group was in the d-block. The roman numerals used correspond to the last digit of today’s naming convention (e.g. the
group 4 elements
were group
IV
B, and the
group 14 elements
were group
I
VA
). In Europe, the lettering was similar, except that “A” was used if the group was before
group 10
, and “B” was used for groups including and after group 10. In addition, groups 8, 9 and 10 used to be treated as one triple-sized group, known collectively in both notations as group V
II
I. In 1988, the new IUPAC naming system was put into use, and the old group names were deprecated.
[20]
Some of these groups have been given
trivial (unsystematic) names
, as seen in the table below, although some are rarely used. Groups 3–10 have no trivial names and are referred to simply by their group numbers or by the name of the first member of their group (such as “the
scandium
group” for
group 3
),[19] since they display fewer similarities and/or vertical trends.
Elements in the same group tend to show patterns in
atomic radius
,
ionization energy
, and
electronegativity
. From top to bottom in a group, the atomic radii of the elements increase. Since there are more filled energy levels,
valence electrons
are found farther from the nucleus. From the top, each successive element has a lower ionization energy because it is easier to remove an electron since the atoms are less tightly bound. Similarly, a group has a top-to-bottom decrease in electronegativity due to an increasing distance between valence electrons and the nucleus.
[21]
There are exceptions to these trends: for example, in
group 11
, electronegativity increases farther down the group.
[22]
hide
· v
· t
· e
Groups in the Periodic table
IUPAC group
1
a
2
3
b
n/a
b
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Mendeleev (I–V
III
)
I
V
VI
VII
VIII
I
II
III
IV
V
VI
VII
c
CAS (US, A-B-A)
IA
IIA
II
IB
I
VB
VIB
V
IIB
V
IIIB
IIIA
IVA
VIA
VIIA
VIIIA
old IUPAC (Europe, A-B)
IA
IIA
IIIA
IVA
VA
VIA
VIIA
VIII
IB
IIB
IIIB
IVB
VB
VIB
VIIB
Trivial name
H and Alkali metals
r
Alkaline earth metals
r
Coinage metals
Triels
Tetrels
Pnictogens
r
Chalcogens
r
Halogens
r
Noble gases
r
Name by elementr
Lithium group
Beryllium group
Scandium group
Titanium group
Vanadium group
Chromium group
Manganese group
Iron group
Cobalt group
Nickel group
Copper group
Zinc group
Boron group
Carbon group
Nitrogen group
Oxygen group
Fluorine group
Helium or Neon group
Period 1
H
He
Period 2
Li
Be
B
C
N
O
F
Ne
Period 3
Na
Mg
Al
Si
P
S
Cl
Ar
Period 4
K
Ca
Sc
Ti
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
Period 5
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
Xe
Period 6
Cs
Ba
La
Ce–Lu
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
Period 7
Fr
Ra
Ac
Th–Lr
Rf
Db
Sg
Bh
Hs
Mt
Ds
Rg
Cn
Nh
Fl
Mc
Lv
Ts
Og
a Group 1 is composed of hydrogen (H) and the alkali metals. Elements of the group have one s-electron in the outer electron shell. Hydrogen is not considered to be an alkali metal as it rarely exhibits behaviour comparable to theirs, though it is more analogous to them than any other group. This makes the group somewhat exceptional.
n/a Do not have a group number
b Group 3 has scandium (Sc) and
yttrium
(Y). For the rest of the group, sources differ as either being (1)
lutetium
(Lu) and lawrencium (Lr), or (2)
lanthanum
(La) and actinium (Ac), or (3) the whole set of 15+15 lanthanides and actinides. IUPAC has initiated a project to standardize the definition as either (1) Sc, Y, Lu and Lr, or (2) Sc, Y, La and Ac.
[23]
c Group 18, the noble gases, were not discovered at the time of Mendeleev’s original table. Later (1902), Mendeleev accepted the evidence for their existence, and they could be placed in a new “group 0”, consistently and without breaking the periodic table principle.
r Group name as recommended by IUPAC.
Periods
Main article:
Period (periodic table)
A period is a horizontal row in the periodic table. Although groups generally have more significant periodic trends, there are regions where horizontal trends are more significant than vertical group trends, such as the f-block, where the lanthanides and actinides form two substantial horizontal series of elements.
[24]
Elements in the same period show trends in atomic radius, ionization energy,
electron affinity
, and electronegativity. Moving left to right across a period, atomic radius usually decreases. This occurs because each successive element has an added proton and electron, which causes the electron to be drawn closer to the nucleus.
[25]
This decrease in atomic radius also causes the ionization energy to increase when moving from left to right across a period. The more tightly bound an element is, the more energy is required to remove an electron. Electronegativity increases in the same manner as ionization energy because of the pull exerted on the electrons by the nucleus.[21] Electron affinity also shows a slight trend across a period. Metals (left side of a period) generally have a lower electron affinity than nonmetals (right side of a period), with the exception of the noble gases.
[26]
Blocks
Main article:
Block (periodic table)
Left to right: s-, f-, d-, p-block in the periodic table
Specific regions of the periodic table can be referred to as blocks in recognition of the sequence in which the
electron shells
of the elements are filled. Elements are assigned to blocks by what orbitals their valence electrons or vacancies lie in.
[27]
The
s-block
comprises the first two groups (alkali metals and
alkaline earth metals
) as well as hydrogen and helium. The p-block comprises the last six groups, which are groups 13 to 18 in IUPAC group numbering (3A to 8A in American group numbering) and contains, among other elements, all of the metalloids. The d-block comprises groups 3 to 12 (or 3B to 2B in American group numbering) and contains all of the transition metals. The f-block, often offset below the rest of the periodic table, has no group numbers and comprises most of the lanthanides and actinides. A hypothetical
g-block
is expected to begin around element 121, a few elements away from what is currently known.
[28]
Metals, metalloids and nonmetals
Metals, metalloids, nonmetals, and elements with unknown chemical properties in the periodic table. Sources disagree on the classification of some of these elements.
According to their shared physical and chemical properties, the elements can be classified into the major categories of metals, metalloids and nonmetals. Metals are generally shiny, highly conducting solids that form alloys with one another and salt-like ionic compounds with nonmetals (other than noble gases). A majority of nonmetals are coloured or colourless insulating gases; nonmetals that form compounds with other nonmetals feature
covalent bonding
. In between metals and nonmetals are metalloids, which have intermediate or mixed properties.
[29]
Metal and nonmetals can be further classified into subcategories that show a gradation from metallic to non-metallic properties, when going left to right in the rows. The metals may be subdivided into the highly reactive alkali metals, through the less reactive alkaline earth metals, lanthanides and actinides, via the archetypal transition metals, and ending in the physically and chemically weak post-transition metals. Nonmetals may be simply subdivided into the
polyatomic nonmetals
, being nearer to the metalloids and show some incipient metallic character; the essentially nonmetallic
diatomic nonmetals
, nonmetallic and the almost completely inert, monatomic noble gases. Specialized groupings such as
refractory metals
and
noble metals
, are examples of subsets of transition metals, also known
[30]
and occasionally denoted.
[31]
Placing elements into categories and subcategories based just on shared properties is imperfect. There is a large disparity of properties within each category with notable overlaps at the boundaries, as is the case with most classification schemes.
[32]
Beryllium, for example, is classified as an alkaline earth metal although its
amphoteric
chemistry and tendency to mostly form covalent compounds are both attributes of a chemically weak or post-transition metal. Radon is classified as a nonmetallic noble gas yet has some cationic chemistry that is characteristic of metals. Other classification schemes are possible such as the division of the elements into
mineralogical occurrence categories
, or
crystalline structures
. Categorizing the elements in this fashion dates back to at least 1869 when
Hinrichs
[33]
wrote that simple boundary lines could be placed on the periodic table to show elements having shared properties, such as metals, nonmetals, or gaseous elements.
Periodic trends and patterns
Main article:
Periodic trends
Electron configuration
Main article:
Electron configuration
Approximate order in which shells and
subshells
are arranged by increasing energy according to the
Madelung rule
The electron configuration or organisation of electrons orbiting neutral atoms shows a recurring pattern or periodicity. The electrons occupy a series of electron shells (numbered 1, 2, and so on). Each shell consists of one or more subshells (named s, p, d, f and g). As atomic number increases, electrons progressively fill these shells and subshells more or less according to the Madelung rule or energy ordering rule, as shown in the diagram. The electron configuration for
neon
, for example, is 1
s2
2s
2 2
p6
. With an atomic number of ten, neon has two electrons in the first shell, and eight electrons in the second shell; there are two electrons in the s subshell and six in the p subshell. In periodic table terms, the first time an electron occupies a new shell corresponds to the start of each new period, these positions being occupied by hydrogen and the alkali metals.
[34]
[35]
Periodic table trends (arrows show an increase)
Since the properties of an element are mostly determined by its electron configuration, the properties of the elements likewise show recurring patterns or periodic behaviour, some examples of which are shown in the diagrams below for atomic radii, ionization energy and electron affinity. It is this periodicity of properties, manifestations of which
were noticed well before
the
underlying theory was developed
, that led to the establishment of the periodic law (the properties of the elements recur at varying intervals) and the formulation of the first periodic tables.[34]
[35]
Atomic radii
Main article:
Atomic radius
Atomic number plotted against atomic radius
[n 3]
Atomic radii vary in a predictable and explainable manner across the periodic table. For instance, the radii generally decrease along each period of the table, from the alkali metals to the noble gases; and increase down each group. The radius increases sharply between the noble gas at the end of each period and the alkali metal at the beginning of the next period. These trends of the atomic radii (and of various other chemical and physical properties of the elements) can be explained by the
electron shell theory
of the atom; they provided important evidence for the development and confirmation of
quantum theory
.
[36]
The electrons in the 4f-subshell, which is progressively filled from lanthanum (element 57) to
ytterbium
(element 70),
[38]
are not particularly effective at shielding the increasing nuclear charge from the sub-shells further out. The elements immediately following the lanthanides have atomic radii that are smaller than would be expected and that are almost identical to the atomic radii of the elements immediately above them.
[39]
Hence lutetium has virtually the same atomic radius (and chemistry) as yttrium,
hafnium
has virtually the same atomic radius (and chemistry) as
zirconium
, and
tantalum
has an atomic radius similar to
niobium
, and so forth. This is an effect of the
lanthanide contraction
: a similar actinide contraction also exists. The effect of the lanthanide contraction is noticeable up to platinum (element 78), after which it is masked by a
relativistic
effect
known as the
inert pair effect
.
[40]
The
d-block contraction
, which is a similar effect between the d-block and p-block, is less pronounced than the lanthanide contraction but arises from a similar cause.[39]
Ionization energy
Ionization energy: each period begins at a minimum for the alkali metals, and ends at a maximum for the noble gases
Main article:
Ionization energy
The first ionization energy is the energy it takes to remove one electron from an atom, the second ionization energy is the energy it takes to remove a second electron from the atom, and so on. For a given atom, successive ionization energies increase with the degree of ionization. For magnesium as an example, the first ionization energy is 738 kJ/mol and the second is 1450 kJ/mol. Electrons in the closer orbitals experience greater forces of electrostatic attraction; thus, their removal requires increasingly more energy. Ionization energy becomes greater up and to the right of the periodic table.[40]
Large jumps in the successive molar ionization energies occur when removing an electron from a noble gas (complete electron shell) configuration. For magnesium again, the first two molar ionization energies of magnesium given above correspond to removing the two 3s electrons, and the third ionization energy is a much larger 7730 kJ/mol, for the removal of a 2p electron from the very stable neon-like configuration of Mg2+. Similar jumps occur in the ionization energies of other third-row atoms.[40]
Electronegativity
Main article:
Electronegativity
Graph showing increasing electronegativity with growing number of selected groups
Electronegativity is the tendency of an atom to attract a shared pair of electrons.
[41]
An atom’s electronegativity is affected by both its atomic number and the distance between the valence electrons and the nucleus. The higher its electronegativity, the more an element attracts electrons. It was first proposed by
Linus Pauling
in 1932.
[42]
In general, electronegativity increases on passing from left to right along a period, and decreases on descending a group. Hence,
fluorine
is the most electronegative of the elements,
[n 4]
while
caesium
is the least, at least of those elements for which substantial data is available.[22]
There are some exceptions to this general rule. Gallium and
germanium
have higher electronegativities than
aluminium
and
silicon
respectively because of the d-block contraction. Elements of the fourth period immediately after the first row of the transition metals have unusually small atomic radii because the 3d-electrons are not effective at shielding the increased nuclear charge, and smaller atomic size correlates with higher electronegativity.[22] The anomalously high electronegativity of lead, particularly when compared to
thallium
and
bismuth
, is an artifact of electronegativity varying with oxidation state: its electronegativity conforms better to trends if it is quoted for the +2 state instead of the +4 state.
[43]
Electron affinity
Main article:
Electron affinity
Dependence of electron affinity on atomic number.
[44]
Values generally increase across each period, culminating with the halogens before decreasing precipitously with the noble gases. Examples of localized peaks seen in hydrogen, the alkali metals and the
group 11 elements
are caused by a tendency to complete the s-shell (with the 6s shell of gold being further stabilized by
relativistic effects
and the presence of a filled 4f sub shell). Examples of localized troughs seen in the alkaline earth metals, and nitrogen, phosphorus, manganese and rhenium are caused by filled s-shells, or half-filled p- or d-shells.
[45]
The electron affinity of an atom is the amount of energy released when an electron is added to a neutral atom to form a negative ion. Although electron affinity varies greatly, some patterns emerge. Generally, nonmetals have more positive electron affinity values than metals. Chlorine most strongly attracts an extra electron. The electron affinities of the noble gases have not been measured conclusively, so they may or may not have slightly negative values.
[46]
Electron affinity generally increases across a period. This is caused by the filling of the valence shell of the atom; a group 17 atom releases more energy than a group 1 atom on gaining an electron because it obtains a filled valence shell and is therefore more stable.[46]
A trend of decreasing electron affinity going down groups would be expected. The additional electron will be entering an orbital farther away from the nucleus. As such this electron would be less attracted to the nucleus and would release less energy when added. In going down a group, around one-third of elements are anomalous, with heavier elements having higher electron affinities than their next lighter congenors. Largely, this is due to the poor shielding by d and f electrons. A uniform decrease in electron affinity only applies to group 1 atoms.
[47]
Metallic character
The lower the values of ionization energy, electronegativity and electron affinity, the more metallic character the element has. Conversely, nonmetallic character increases with higher values of these properties.
[48]
Given the periodic trends of these three properties, metallic character tends to decrease going across a period (or row) and, with some irregularities (mostly) due to poor screening of the nucleus by d and f electrons, and relativistic effects,
[49]
tends to increase going down a group (or column or family). Thus, the most metallic elements (such as caesium and francium) are found at the bottom left of traditional periodic tables and the most nonmetallic elements (oxygen, fluorine, chlorine) at the top right. The combination of horizontal and vertical trends in metallic character explains the stair-shaped
dividing line between metals and nonmetals
found on some periodic tables, and the practice of sometimes categorizing several elements adjacent to that line, or elements adjacent to those elements, as metalloids.
[50]
[51]
Oxidation number
With some minor exceptions,
oxidation numbers
among the elements show four main trends according to their periodic table geographic location: left; middle; right; and south. On the left (groups 1 to 3), the highest most stable oxidation number is the group number, with lower oxidation states being less stable. In the middle (groups 4 to 11), higher oxidation states become more stable going down each group. Group 12 is an exception to this trend; they behave as if they were located on the left side of the table. On the right, higher oxidation states tend to become less stable going down a group.
[52]
The shift between these trends is continuous: for example, group 3 also has lower oxidation states most stable in its lightest member (scandium, with CsScCl3 for example known in the +2 state),
[53]
and group 12 is predicted to have
copernicium
more readily showing oxidation states above +2.
[54]
The lanthanides and actinides positioned along the south of the table are distinguished by having the +3 oxidation state in common; this is the most stable state for the lanthanides. The early actinides show a pattern of oxidation states somewhat similar to those of their period 6 and 7 transition metal congeners; the later actinides are more similar to the lanthanides.
[55]
Linking or bridging groups
Sc, Y, La, Ac, Zr, Hf, Rf, Nb, Ta, Db, Lu, Lr, Cu, Ag, Au, Zn, Cd, Hg, He, Ne, Ar, Kr, Xe, Rn
Hydrogen |
Helium |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Lithium |
Beryllium |
Boron |
Carbon |
Nitrogen |
Oxygen |
Fluorine |
Neon |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Sodium |
Magnesium |
Aluminium |
Silicon |
Phosphorus |
Sulfur |
Chlorine |
Argon |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Potassium |
Calcium |
Scandium |
Titanium |
Vanadium |
Chromium |
Manganese |
Iron |
Cobalt |
Nickel |
Copper |
Zinc |
Gallium |
Germanium |
Arsenic |
Selenium |
Bromine |
Krypton |
||||||||||||||||||||||||||||||||||||||||||||||
Rubidium |
Strontium |
Yttrium |
Zirconium |
Niobium |
Molybdenum |
Technetium |
Ruthenium |
Rhodium |
Palladium |
Silver |
Cadmium |
Indium |
Tin |
Antimony |
Tellurium |
Iodine |
Xenon |
||||||||||||||||||||||||||||||||||||||||||||||
Caesium |
Barium |
Lanthanum |
Cerium |
Praseodymium |
Neodymium |
Promethium |
Samarium |
Europium |
Gadolinium |
Terbium |
Dysprosium |
Holmium |
Erbium |
Thulium |
Ytterbium |
Lutetium |
Hafnium |
Tantalum |
Tungsten |
Rhenium |
Osmium |
Iridium |
Platinum |
Gold |
Mercury (element) |
Thallium |
Lead |
Bismuth |
Polonium |
Astatine |
Radon |
||||||||||||||||||||||||||||||||
Francium |
Radium |
Actinium |
Thorium |
Protactinium |
Uranium |
Neptunium |
Plutonium |
Americium |
Curium |
Berkelium |
Californium |
Einsteinium |
Fermium |
Mendelevium |
Nobelium |
Lawrencium |
Rutherfordium |
Dubnium |
Seaborgium |
Bohrium |
Hassium |
Meitnerium |
Darmstadtium |
Roentgenium |
Copernicium |
Nihonium |
Flerovium |
Moscovium |
Livermorium |
Tennessine |
Oganesson |
32-column periodic table showing, from left to right, the location of group 3; the heavy group 4 and 5 elements; lutetium and lawrencium; groups 11–12; and the noble gases
From left to right across the four blocks of the long- or 32-column form of the periodic table are a series of linking or bridging groups of elements, located approximately between each block. In general, groups at the peripheries of blocks display similarities to the groups of the neighbouring blocks as well as to the other groups in their own blocks, as expected as most periodic trends are continuous.
[56]
These groups, like the metalloids, show properties in between, or that are a mixture of, groups to either side. Chemically, the
group 3 elements
, lanthanides, and heavy group 4 and 5 elements show some behaviour similar to the alkaline earth metals
[57]
or, more generally, s block metals
[58]
[59]
[60]
but have some of the physical properties of d block transition metals;
[61]
meanwhile, lutetium behaves chemically as a lanthanide (with which it is often classified) but shows a mix of lanthanide and transition metal physical properties (as does yttrium).
[62]
[63]
Lawrencium, as an analogue of lutetium, would presumably display like characteristics.
[n 5]
The coinage metals in group 11 (copper, silver, and gold) are chemically capable of acting as either transition metals or main group metals.
[66]
The volatile group 12 metals, zinc, cadmium and mercury are sometimes regarded as linking the d block to the p block. Notionally they are d block elements but they have few transition metal properties and are more like their p block neighbors in group 13.
[67]
[68]
The relatively inert noble gases, in group 18, bridge the most reactive groups of elements in the periodic table—the halogens in group 17 and the alkali metals in group 1.[56]
History
Main article:
History of the periodic table
First systemization attempts
The
discovery of the elements
mapped to significant periodic table development dates (pre-, per- and post-)
In 1789,
Antoine Lavoisier
published a list of 33 chemical elements, grouping them into gases, metals, nonmetals, and
earths
.
[69]
Chemists spent the following century searching for a more precise classification scheme. In 1829,
Johann Wolfgang Döbereiner
observed that many of the elements could be grouped into triads based on their chemical properties. Lithium, sodium, and
potassium
, for example, were grouped together in a triad as soft, reactive metals. Döbereiner also observed that, when arranged by atomic weight, the second member of each triad was roughly the average of the first and the third.
[70]
This became known as the
Law of Triads
.
[71]
German chemist
Leopold Gmelin
worked with this system, and by 1843 he had identified ten triads, three groups of four, and one group of five.
Jean-Baptiste Dumas
published work in 1857 describing relationships between various groups of metals. Although various chemists were able to identify relationships between small groups of elements, they had yet to build one scheme that encompassed them all.[70] In 1857, German chemist
August Kekulé
observed that carbon often has four other atoms bonded to it.
Methane
, for example, has one carbon atom and four hydrogen atoms.
[72]
This concept eventually became known as
valency
, where different elements bond with different numbers of atoms.
[73]
In 1862, the French geologist
Alexandre-Émile Béguyer de Chancourtois
published an early form of the periodic table, which he called the telluric helix or screw. He was the first person to notice the periodicity of the elements. With the elements arranged in a spiral on a cylinder by order of increasing atomic weight, de Chancourtois showed that elements with similar properties seemed to occur at regular intervals. His chart included some ions and compounds in addition to elements. His paper also used geological rather than chemical terms and did not include a diagram. As a result, it received little attention until the work of Dmitri Mendeleev.
[74]
Julius Lothar Meyer
‘s periodic table, published in “Die modernen Theorien der Chemie” (1864)
[75]
In 1864, Julius Lothar Meyer, a German chemist, published a table with 28 elements. Realizing that an arrangement according to atomic weight did not exactly fit the observed periodicity in chemical properties he gave valency priority over minor differences in atomic weight. A missing element between Si and Sn was predicted with atomic weight 73 and valency 4.[75] Concurrently, English chemist
William Odling
published an arrangement of 57 elements, ordered on the basis of their
atomic weights
. With some irregularities and gaps, he noticed what appeared to be a periodicity of atomic weights among the elements and that this accorded with “their usually received groupings”.
[76]
Odling alluded to the idea of a periodic law but did not pursue it.
[77]
He subsequently proposed (in 1870) a valence-based classification of the elements.
[78]
Newlands’
periodic table, as presented to the
Chemical Society
in 1866, and based on the law of
octaves
English chemist
John Newlands
produced a series of papers from 1863 to 1866 noting that when the elements were listed in order of increasing atomic weight, similar physical and chemical properties recurred at intervals of eight. He likened such periodicity to the octaves of music.
[79]
[80]
This so termed
Law of Octaves
was ridiculed by Newlands’ contemporaries, and the Chemical Society refused to publish his work.
[81]
Newlands was nonetheless able to draft a table of the elements and used it to predict the existence of
missing elements
, such as germanium.
[82]
The Chemical Society only acknowledged the significance of his discoveries five years after they credited Mendeleev.
[83]
In 1867,
Gustavus Hinrichs
, a Danish born academic chemist based in America, published a spiral periodic system based on atomic spectra and weights, and chemical similarities. His work was regarded as idiosyncratic, ostentatious and labyrinthine and this may have militated against its recognition and acceptance.
[84]
[85]
Mendeleev’s table
Periodic table of elements.
Vienna
,
1885
.
University of St Andrews
Mendeleev’s periodic table from his book An Attempt Towards a Chemical Conception of the Ether
A version of Mendeleev’s 1869 periodic table: An experiment on a system of elements based on their atomic weights and chemical similarities. This early arrangement presents the periods vertically and the groups horizontally.
Russian chemistry professor Dmitri Mendeleev and German chemist Julius Lothar Meyer independently published their periodic tables in 1869 and 1870, respectively.
[86]
Mendeleev’s table, dated March 1 [
O.S.
February 17] 1869,
[87]
was his first published version. That of Meyer was an expanded version of his (Meyer’s) table of 1864.
[88]
They both constructed their tables by listing the elements in rows or columns in order of atomic weight and starting a new row or column when the characteristics of the elements began to repeat.
[89]
The recognition and acceptance afforded to Mendeleev’s table came from two decisions he made. The first was to leave gaps in the table when it seemed that the corresponding element had not yet been discovered.
[90]
Mendeleev was not the first chemist to do so, but he was the first to be recognized as using the trends in his periodic table to predict the properties of those missing elements, such as
gallium
and germanium.
[91]
The second decision was to occasionally ignore the order suggested by the atomic weights and switch adjacent elements, such as
tellurium
and
iodine
, to better classify them into
chemical families
.
Mendeleev published in 1869, using atomic weight to organize the elements, information determinable to fair precision in his time. Atomic weight worked well enough to allow Mendeleev to accurately predict the properties of missing elements.
Mendeleev took the unusual step of naming missing elements using the
Sanskrit
numerals eka (1), dvi (2), and tri (3) to indicate that the element in question was one, two, or three rows removed from a lighter congener. It has been suggested that Mendeleev, in
doi
ng so, was paying homage to ancient
Sanskrit grammarians
, in particular
Pāṇini
, who devised a periodic alphabet for the language.
[92]
Henry Moseley
(1887–1915)
Following the discovery of the atomic nucleus by
Ernest Rutherford
in 1911, it was proposed that the integer count of the nuclear charge is identical to the sequential place of each element in the periodic table. In 1913, English physicist Henry Moseley using
X-ray spectroscopy
confirmed this proposal experimentally. Moseley determined the value of the nuclear charge of each element and showed that Mendeleev’s ordering actually places the elements in sequential order by nuclear charge.
[93]
Nuclear charge is identical to proton count and determines the value of the atomic number (Z) of each element. Using atomic number gives a definitive, integer-based sequence for the elements. Moseley predicted, in 1913, that the only elements still missing between aluminium (Z = 13) and gold (Z = 79) were Z = 43, 61, 72, and 75, all of which were later discovered. The atomic number is the absolute definition of an element and gives a factual basis for the ordering of the periodic table.
[94]
Second version and further development
Mendeleev’s 1871 periodic table with eight groups of elements. Dashes represented elements unknown in 1871.
Eight-group form of periodic table, updated with all elements discovered to 2016
In 1871, Mendeleev published his periodic table in a new form, with groups of similar elements arranged in columns rather than in rows, and those columns numbered I to VIII corresponding with the element’s oxidation state. He also gave detailed predictions for the properties of elements he had earlier noted were missing, but should exist.
[95]
These gaps were subsequently filled as chemists discovered additional naturally occurring elements.
[96]
It is often stated that the last naturally occurring element to be discovered was francium (referred to by Mendeleev as eka-caesium) in 1939, but it was technically only the last element to be discovered in nature as opposed to by synthesis.[97] Plutonium, produced synthetically in 1940, was identified in trace quantities as a naturally occurring element in 1971.
[98]
The popular
[99]
periodic table layout, also known as the common or standard form (as shown at various other points in this article), is attributable to Horace Groves Deming. In 1923, Deming, an American chemist, published short (
Mendeleev style
) and medium (
18-column
) form periodic tables.
[100]
[n 6]
Merck and Company prepared a handout form of Deming’s 18-column medium table, in 1928, which was widely circulated in American schools. By the 1930s Deming’s table was appearing in handbooks and encyclopedias of chemistry. It was also distributed for many years by the Sargent-Welch Scientific Company.
[101]
[102]
[103]
With the development of modern quantum mechanical theories of electron configurations within atoms, it became apparent that each period (row) in the table corresponded to the filling of a
quantum shell
of electrons. Larger atoms have more electron sub-shells, so later tables have required progressively longer periods.
[104]
Glenn T. Seaborg
, in 1945, suggested a new periodic table showing the actinides as belonging to a second f-block series.
In 1945,
Glenn Seaborg
, an American scientist, made the
suggestion
that the
actinide elements
, like the lanthanides, were filling an f sub-level. Before this time the actinides were thought to be forming a fourth d-block row. Seaborg’s colleagues advised him not to publish such a radical suggestion as it would most likely ruin his career. As Seaborg considered he did not then have a career to bring into disrepute, he published anyway. Seaborg’s suggestion was found to be correct and he subsequently went on to win the 1951
Nobel Prize
in chemistry for his work in synthesizing actinide elements.
[105]
[106]
[n 7]
Although minute quantities of some
transuranic elements
occur naturally,[3] they were all first discovered in laboratories. Their production has expanded the periodic table significantly, the first of these being
neptunium
, synthesized in 1939.
[107]
Because many of the transuranic elements are highly unstable and decay quickly, they are challenging to detect and characterize when produced. There have been controversies concerning the acceptance of competing discovery claims for some elements, requiring independent review to determine which party has priority, and hence naming rights.
[108]
In 2010, a joint Russia–US collaboration at
Dubna
,
Moscow Oblast
, Russia, claimed to have synthesized six atoms of tennessine (element 117), making it the most recently claimed discovery. It, along with nihonium (element 113), moscovium (element 115), and oganesson (element 118), are the four most recently named elements, whose names all became official on 28 November 2016.
[109]
Different periodic tables
The long- or 32-column table
The periodic table in 32-column format
The modern periodic table is sometimes expanded into its long or 32-column form by reinstating the footnoted f-block elements into their natural position between the s- and d-blocks, as proposed by
Alfred Werner
.
[110]
Unlike the 18-column form this arrangement results in “no interruptions in the sequence of increasing atomic numbers”.
[111]
The relationship of the f-block to the other blocks of the periodic table also becomes easier to see.
[112]
Jensen
advocates a form of table with 32 columns on the grounds that the lanthanides and actinides are otherwise relegated in the minds of students as dull, unimportant elements that can be quarantined and ignored.
[113]
Despite these advantages the 32-column form is generally avoided by editors on account of its undue rectangular ratio compared to a book page ratio,
[114]
and the familiarity of chemists with the modern form, as introduced by Seaborg.
[115]
show
· v
· t
· e
Periodic table (large cells, 32-column layout)
Tables with different structures
Main article:
Alternative periodic tables
Within 100 years of the appearance of Mendeleev’s table in 1869,
Edward G. Mazurs
had collected an estimated 700 different published versions of the periodic table.[113]
[118]
[
119
]
As well as numerous rectangular variations, other periodic table formats have been shaped, for example,
[n 8]
like a circle, cube, cylinder, building, spiral,
lemniscate
,
[
120
]
octagonal prism, pyramid, sphere, or triangle. Such alternatives are often developed to highlight or emphasize chemical or physical properties of the elements that are not as apparent in traditional periodic tables.[119]
Theodor Benfey’s spiral periodic table
A popular
[121]
alternative structure is that of
Otto Theodor Benfey
(1960). The elements are arranged in a continuous spiral, with hydrogen at the centre and the transition metals, lanthanides, and actinides occupying peninsulas.
[122]
Most periodic tables are two-dimensional;[3] three-dimensional tables are known to as far back as at least 1862 (pre-dating Mendeleev’s two-dimensional table of 1869). More recent examples include Courtines’ Periodic Classification (1925),
[123]
Wringley’s Lamina System (1949),
[124]
Giguère
‘s Periodic helix (1965)
[125]
and Dufour’s Periodic Tree (1996).
[126]
Going one further, Stowe’s Physicist’s Periodic Table (1989)
[127]
has been described as being four-dimensional (having three spatial dimensions and one colour dimension).
[128]
The various forms of periodic tables can be thought of as lying on a chemistry–physics continuum.
[129]
Towards the chemistry end of the continuum can be found, as an example, Rayner-Canham’s “unruly”
[130]
Inorganic Chemist’s Periodic Table (2002),
[131]
which emphasizes trends and patterns, and unusual chemical relationships and properties. Near the physics end of the continuum is
Janet
‘s Left-Step Periodic Table (1928). This has a structure that shows a closer connection to the order of electron-shell filling and, by association,
quantum mechanics
.
[132]
A somewhat similar approach has been taken by Alper,
[133]
albeit criticized by
Eric
Scerri
as disregarding the need to display chemical and physical periodicity.
[134]
Somewhere in the middle of the continuum is the ubiquitous common or standard form of periodic table. This is regarded as better expressing empirical trends in physical state, electrical and thermal conductivity, and oxidation numbers, and other properties easily inferred from traditional techniques of the chemical laboratory.
[135]
Its popularity is thought to be a result of this layout having a good balance of features in terms of ease of construction and size, and its depiction of atomic order and periodic trends.[77]
[136]
hide
· v
· t
· e
Left-step periodic table (by Charles Janet)
f1 |
f2 |
f3 |
f4 |
f5 |
f6 |
f7 |
f8 |
f9 |
f10 |
f11 |
f12 |
f13 |
f14 |
d1 |
d2 |
d3 |
d4 |
d5 |
d6 |
d7 | d8 |
d9 |
d10 |
p1 |
p2 |
p3 |
p4 |
p5 |
p6 |
s1 |
s2 |
1s |
H |
||||||||||||||||||||||||||||||
2s | |||||||||||||||||||||||||||||||
2p 3s |
|||||||||||||||||||||||||||||||
3p 4s |
|||||||||||||||||||||||||||||||
3d 4p 5s |
|||||||||||||||||||||||||||||||
4d 5p 6s |
I |
||||||||||||||||||||||||||||||
4f 5d 6p 7s |
Ce |
Pr |
Nd |
Pm |
Sm |
Eu |
Gd |
Tb |
Dy |
Ho |
Er |
Tm |
Yb |
Lu |
|||||||||||||||||
5f 6d 7p 8s |
Th |
Pa |
U |
Np |
Pu |
Am |
Cm |
Bk |
Cf |
Es |
Fm |
Md |
No |
Lr |
119 |
120 |
|||||||||||||||
f-block |
d-block |
p-block |
s-block |
This form of periodic table is congruent with the order in which electron shells are ideally filled according to the Madelung rule, as shown in the accompanying sequence in the left margin (read from top to bottom, left to right). The experimentally determined ground-state electron configurations of the elements differ from the configurations predicted by the Madelung rule in twenty instances, but the Madelung-predicted configurations are always at least close to the ground state. The last two elements shown, elements 119 and 120, have not yet been synthesized.
Open questions and controversies
Placement of hydrogen and helium
Simply following electron configurations, hydrogen (electronic configuration 1s1) and helium (1s2) should be placed in groups 1 and 2, above lithium (1s22s1) and beryllium (1s22s2).
[137]
While such a placement is common for hydrogen, it is rarely used for helium outside of the context of electron configurations: When the noble gases (then called “inert gases”) were first discovered around 1900, they were known as “group 0”, reflecting no chemical reactivity of these elements known at that point, and helium was placed on the top of that group, as it did share the extreme chemical inertness seen throughout the group. As the group changed its formal number, many authors continued to assign helium directly above neon, in group 18; one of the examples of such placing is the current IUPAC table.
[138]
The position of hydrogen in group 1 is reasonably well settled. Its usual oxidation state is +1 as is the case for its heavier alkali metal congeners. Like lithium, it has a significant covalent chemistry.
[139]
[140]
It can stand in for alkali metals in typical alkali metal structures.
[141]
It is capable of forming alloy-like hydrides, featuring metallic bonding, with some transition metals.
[142]
Nevertheless, it is sometimes placed elsewhere. A common alternative is at the top of group 17[134] given hydrogen’s strictly univalent and largely non-metallic chemistry, and the strictly univalent and non-metallic chemistry of fluorine (the element otherwise at the top of group 17). Sometimes, to show hydrogen has properties corresponding to both those of the alkali metals and the halogens, it is shown at the top of the two columns simultaneously.
[143]
Another suggestion is above carbon in group 14: placed that way, it fits well into the trends of increasing ionization potential values and electron affinity values, and is not too far from the electronegativity trend, even though hydrogen cannot show the
tetravalence
characteristic of the heavier group 14 elements.
[144]
Finally, hydrogen is sometimes placed separately from any group; this is based on its general properties being regarded as sufficiently different from those of the elements in any other group.
The other period 1 element, helium, is most often placed in group 18 with the other noble gases, as its extraordinary inertness is extremely close to that of the other light noble gases neon and argon.[145] Nevertheless, it is occasionally placed separately from any group as well.
[146]
The property that distinguishes helium from the rest of the noble gases is that in its closed electron shell, helium has only two electrons in the outermost electron orbital, while the rest of the noble gases have eight. Some authors, such as
Henry Bent
(the eponym of
Bent’s rule
),
Wojciech Grochala
, and
Felice Grandinetti
, have argued that helium would be correctly placed in group 2, over beryllium; Charles Janet’s left-step table also contains this assignment. The normalized ionization potentials and electron affinities show better trends with helium in group 2 than in group 18; helium is expected to be slightly more reactive than neon (which breaks the general trend of reactivity in the noble gases, where the heavier ones are more reactive); predicted helium compounds often lack neon analogues even theoretically, but sometimes have beryllium analogues; and helium over beryllium better follows the trend of first-row anomalies in the table (s >> p > d > f).
[147]
[148]
[149]
Group 3 and its elements in periods 6 and 7
Although scandium and yttrium are always the first two elements in group 3, the identity of the next two elements is not completely settled. They are commonly lanthanum and actinium, and less often lutetium and lawrencium. The two variants originate from historical difficulties in placing the lanthanides in the periodic table, and arguments as to where the f block elements start and end.
[150]
[n 9]
It has been claimed that such arguments are proof that, “it is a mistake to break the [periodic] system into sharply delimited blocks”.
[151]
A third common variant shows the two positions below yttrium as being occupied by the lanthanides and the actinides.[29]
Chemical and physical arguments have been made in support of lutetium and lawrencium
[152]
[153]
but the majority of authors seem either unconvinced by them or unaware of them.
[154]
[155]
Most working chemists are not aware there is any controversy.[155] In December 2015 an IUPAC project was established to make a recommendation on the matter, considering only the first two alternatives as possibilities.
[156]
Lanthanum and actinium
La and Ac below Y |
Lanthanum and actinium are commonly depicted as the remaining group 3 members.
[157]
[n 10]
It has been suggested that this layout originated in the 1940s, with the appearance of periodic tables relying on the ground-state electron configurations of the elements and the notion of the differentiating electron. The ground-state configurations of caesium,
barium
and lanthanum are [Xe]6s1, [Xe]6s2 and [Xe]5d16s2. Lanthanum thus emerges with a 5d differentiating electron and on these grounds it was considered to be “in group 3 as the first member of the d-block for period 6”.
[158]
A superficially consistent set of electron configurations is then seen in group 3: scandium [Ar]3d14s2, yttrium [Kr]4d15s2 and lanthanum [Xe]5d16s2. Still in period 6, ytterbium was assigned an electron configuration of [Xe]4f135d16s2 and lutetium [Xe]4f145d16s2, “resulting in a 4f differentiating electron for lutetium and firmly establishing it as the last member of the f-block for period 6”.[158] Later
spectroscopic
work found that the electron configuration of ytterbium was in fact [Xe]4f146s2. This meant that ytterbium and lutetium—the latter with [Xe]4f145d16s2—both had 14 f-electrons, “resulting in a d- rather than an f- differentiating electron” for lutetium and making it an “equally valid candidate” with [Xe]5d16s2 lanthanum, for the group 3 periodic table position below yttrium.[158] Lanthanum has the advantage of incumbency since the 5d1 electron appears for the first time in its structure whereas it appears for the third time in lutetium, having also made a brief second appearance in gadolinium
[159]
(though similar logic would also lead to thorium getting the 6d2 position, having incumbency over
rutherfordium
).
In terms of chemical behaviour,
[160]
and trends going down group 3 (if Sc-Y-La is chosen) for properties such as melting point, electronegativity and ionic radius,
[161]
[162]
scandium, yttrium, lanthanum and actinium are similar to their group 1–2 counterparts. In this variant, the number of f electrons in the most common (trivalent) ions of the f-block elements consistently matches their position in the f-block.
[163]
For example, the f-electron counts for the trivalent ions of the first three f-block elements are Ce 1, Pr 2 and Nd 3.
[164]
However, outside the lanthanides there does not exist a typical oxidation state across any period of a block.[36]
Lutetium and lawrencium
Lu and Lr below Y |
In other tables, lutetium and lawrencium are the remaining group 3 members.
[n 11]
Early techniques for chemically separating scandium, yttrium and lutetium relied on the fact that these elements occurred together in the so-called “yttrium group” whereas La and Ac occurred together in the “cerium group”.[158] Accordingly, lutetium rather than lanthanum was assigned to group 3 by some chemists in the 1920s and 30s.
[n 12]
Several physicists in the 1950s and ’60s favoured lutetium, in light of a comparison of several of its physical properties with those of lanthanum.[158]
This arrangement, in which lanthanum is the first member of the f-block, is disputed by some authors since lanthanum lacks any f-electrons. It has been argued that this is not a valid concern given other periodic table anomalies—thorium, for example, has no f-electrons yet is part of the f-block.
[165]
Karl Gschneidner, analysing the melting points of the lanthanides in a 1971 article, reached the conclusion that it was likely that 4f, 5d, 6s, and 6p electrons were all involved in the bonding of lanthanide metals except for lutetium.
[166]
The fact that lanthanum was demonstrated to be a 4f-band metal (with about 0.17 electrons per atom)
[37]
whereas the 4f shell appears to have no influence on the metallic properties of lutetium, has been used as an argument to place lutetium in group 3 instead of lanthanum.
[167]
Scandium, yttrium, and lutetium show a more consistent set of electron configurations matching the global trend on the periodic table: the 5d metals then all add a closed 4f14 shell. (For example, the shift from yttrium [Kr]4d15s2 to lutetium [Xe]4f145d16s2 exactly parallels that from zirconium [Kr]4d25s2 to hafnium [Xe]4f145d26s2.)[158] The inclusion of lutetium rather than lanthanum also homogenises the 5d transition series: trends in atomic size, coordination number, and relative abundance of metal–oxygen bonds all reveal that lutetium is closer than lanthanum to the behaviour of the uncontroversial 5d metals hafnium through mercury.
[168]
As for lawrencium, its gas phase ground-state atomic electron configuration was confirmed in 2015 as [Rn]5f147s27p1. Such a configuration represents another periodic table anomaly, regardless of whether lawrencium is located in the f-block or the d-block, as the only potentially applicable p-block position has been reserved for nihonium with its predicted configuration of [Rn]5f146d107s27p1.
[169]
However, it is expected that in the condensed phase and in chemical environments lawrencium has the expected 6d occupancy, and simple modelling studies suggest it will behave like a lanthanide,
[170]
as do the rest of the late actinides, in particular being a homologue of lutetium.[164]
While scandium, yttrium and lutetium (and presumably lawrencium) do often behave like trivalent versions of the group 1–2 metals, being hard class-A cations mostly restricted to the group oxidation state, they are not the only elements in the d-block or f-block that do so. The early transition metals zirconium and hafnium in group 4 also display such behaviour, as does the actinide thorium.
[171]
[172]
The physical properties of the group 3 elements are affected by the presence of a d electron, which forms more localised bonds within the metals than the p electrons in the similar group 13 metals;[61] exactly the same situation is found comparing group 4 to group 14.[60] Trends going down group 3 (if Sc-Y-Lu is chosen) for properties such as melting point, electronegativity and ionic radius, are similar to those found among their group 4–8 counterparts.[158] In this variant, the number of f electrons in the gaseous forms of the f-block atoms usually matches their position in the f-block. For example, the f-electron counts for the first five f-block elements are La 0, Ce 1, Pr 3, Nd 4 and Pm 5.[158]
Lanthanides and actinides
Markers below Y |
A few authors position all thirty lanthanides and actinides in the two positions below yttrium (usually via footnote markers). This variant, which is stated in the 2005
Red Book
to be the IUPAC-agreed version as of 2005 (a number of later versions exist, and the last update is from 1 December 2018),
[173]
[n 13]
emphasizes similarities in the chemistry of the 15 lanthanide elements (La–Lu), possibly at the expense of ambiguity as to which elements occupy the two group 3 positions below yttrium, and a 15-column wide f block (there can only be 14 elements in any row of the f block).
[n 14]
Groups included in the transition metals
The definition of a transition metal, as given by IUPAC in the Gold Book, is an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell.
[175]
By this definition all of the elements in groups 3–11 are transition metals. The IUPAC definition therefore excludes group 12, comprising zinc, cadmium and mercury, from the transition metals category. However, the 2005
IUPAC nomenclature
as codified in the Red Book gives both the group 3–11 and group 3–12 definitions of the transition metals as alternatives.
Some chemists treat the categories “d-block elements” and “transition metals” interchangeably, thereby including groups 3–12 among the transition metals. In this instance the group 12 elements are treated as a special case of transition metal in which the d electrons are not ordinarily given up for chemical bonding (they can sometimes contribute to the valence bonding orbitals even so, as in
zinc fluoride
).
[176]
The 2007 report of
mercury(IV) fluoride
(HgF4), a compound in which mercury would use its d electrons for bonding, has prompted some commentators to suggest that mercury can be regarded as a transition metal.
[177]
Other commentators, such as Jensen,
[178]
have argued that the formation of a compound like HgF4 can occur only under highly abnormal conditions; indeed, its existence is currently disputed. As such, mercury could not be regarded as a transition metal by any reasonable interpretation of the ordinary meaning of the term.[178]
Still other chemists further exclude the group 3 elements from the definition of a transition metal. They do so on the basis that the group 3 elements do not form any ions having a partially occupied d shell and do not therefore exhibit properties characteristic of transition metal chemistry.
[179]
In this case, only groups 4–11 are regarded as transition metals. This categorisation is however not one of the alternatives considered by IUPAC. Though the group 3 elements show few of the characteristic chemical properties of the transition metals, the same is true of the heavy members of groups 4 and 5, which also are mostly restricted to the group oxidation state in their chemistry. Moreover, the group 3 elements show characteristic physical properties of transition metals (on account of the presence in each atom of a single d electron).[61]
Elements with unknown chemical properties
Although all elements up to oganesson have been discovered, of the elements above
hassium
(element 108), only copernicium (element 112), nihonium (element 113), and
flerovium
(element 114) have known chemical properties, and only for copernicium is there enough evidence for a conclusive categorisation at present. The other elements may behave differently from what would be predicted by extrapolation, due to relativistic effects; for example, flerovium has been predicted to possibly exhibit some noble-gas-like properties, even though it is currently placed in the
carbon group
.
[180]
The current experimental evidence still leaves open the question of whether flerovium behaves more like a metal or a noble gas.
[181]
Further periodic table extensions
Main article:
Extended periodic table
Ununennium |
Unbinilium |
Unbiunium |
Unquadquadium |
Unquadpentium |
Unquadhexium |
Unquadseptium |
Unquadoctium |
Unquadennium |
Unpentnilium |
Unpentunium |
Unpentbium |
Unpenttrium |
Unpentquadium |
Unpentpentium |
Unpenthexium |
Unpentseptium |
Unpentoctium |
Unpentennium |
Unhexnilium |
Unhexunium |
Unhexbium |
Unhextrium |
Unhexquadium |
Unhexpentium |
Unhexhexium |
Unhexseptium |
Unhexoctium |
Unhexennium |
Unseptnilium |
Unseptunium |
Unseptbium |
Unbibium |
Unbitrium |
Unbiquadium |
Unbipentium |
Unbihexium |
Unbiseptium |
Unbioctium |
Unbiennium |
Untrinilium |
Untriunium |
Untribium |
Untritrium |
Untriquadium |
Untripentium |
Untrihexium |
Untriseptium |
Untrioctium |
Untriennium |
Unquadnilium |
Unquadunium |
Unquadbium |
Unquadtrium |
Periodic table with eight rows, extended to element 172
[182]
It is unclear whether new elements will continue the pattern of the current periodic table as
period 8
, or require further adaptations or adjustments. Seaborg expected the eighth period to follow the previously established pattern exactly, so that it would include a two-element s-block for elements 119 and 120, a new g-block for the next 18 elements, and 30 additional elements continuing the current f-, d-, and p-blocks, culminating in element 168, the next noble gas.
[183]
More recently, physicists such as
Pekka Pyykkö
have theorized that these additional elements do not exactly follow the Madelung rule, which predicts how electron shells are filled and thus affects the appearance of the present periodic table. There are currently several competing theoretical models for the placement of the elements of atomic number less than or equal to 172. In all of these it is element 172, rather than element 168, that emerges as the next noble gas after oganesson, although these must be regarded as speculative as no complete calculations have been done beyond element 123.
[184]
[185]
Element with the highest possible atomic number
The number of possible elements is not known. A very early suggestion made by Elliot Adams in 1911, and based on the arrangement of elements in each horizontal periodic table row, was that elements of atomic weight greater than circa 256 (which would equate to between elements 99 and 100 in modern-day terms) did not exist.
[186]
A higher, more recent estimate is that the periodic table may end soon after the
island of stability
,
[187]
whose centre is predicted to lie between
element 110
and
element 126
, as the extension of the periodic and
nuclide tables
is restricted by proton and neutron
drip lines
as well as decreasing stability towards
spontaneous fission
.
[188]
[189]
Other predictions of an end to the periodic table include at element 128 by
John Emsley
,[3] at element 137 by
Richard Feynman
,
[190]
at element 146 by Yogendra Gambhir,
[191]
and at element 155 by Albert Khazan.[3]
[n 15]
Bohr model
The Bohr model exhibits difficulty for atoms with atomic number greater than 137, as any element with an atomic number greater than 137 would require 1s electrons to be travelling faster than c, the
speed of light
.
[192]
Hence the non-relativistic Bohr model is inaccurate when applied to such an element.
Relativistic Dirac equation
The relativistic Dirac equation has problems for elements with more than 137 protons. For such elements, the wave function of the Dirac ground state is oscillatory rather than bound, and there is no gap between the positive and negative energy spectra, as in the
Klein paradox
.
[193]
More accurate calculations taking into account the effects of the finite size of the nucleus indicate that the binding energy first exceeds the limit for elements with more than 173 protons. For heavier elements, if the innermost orbital (1s) is not filled, the electric field of the nucleus will pull an electron out of the vacuum, resulting in the
spontaneous emission of a positron
.
[194]
This does not happen if the innermost orbital is filled, so that element 173 is not necessarily the end of the periodic table.[190]
Optimal form
The many different forms of periodic table have prompted the question of whether there is an optimal or definitive form of periodic table.
[195]
The answer to this question is thought to depend on whether the chemical periodicity seen to occur among the elements has an underlying truth, effectively hard-wired into the universe, or if any such periodicity is instead the product of subjective human interpretation, contingent upon the circumstances, beliefs and predilections of human observers. An objective basis for chemical periodicity would settle the questions about the location of hydrogen and helium, and the composition of group 3. Such an underlying truth, if it exists, is thought to have not yet been discovered. In its absence, the many different forms of periodic table can be regarded as variations on the theme of chemical periodicity, each of which explores and emphasizes different aspects, properties, perspectives and relationships of and among the elements.
[n 16]
Other
In celebration of the periodic table’s 150th anniversary, the
United Nations
declared the year 2019 as the International Year of the Periodic Table, celebrating “one of the most significant achievements in science”.
[198]
See also
·
Chemistry portal
·
Abundance of the chemical elements
·
Atomic electron configuration table
·
Element collecting
· List of chemical elements
·
List of periodic table-related articles
·
Names for sets of chemical elements
·
Standard model
·
Table of nuclides
·
Template:Spectral lines of the elements
·
The Mystery of Matter:
Search
for the Elements (PBS film)
·
Timeline of chemical element discoveries
Notes
1.
^
The elements discovered initially by synthesis and later in nature are technetium (Z = 43), promethium (61), astatine (85), neptunium (93), and plutonium (94).
2.
^
An
element zero
(i.e. a substance composed purely of neutrons), is included in a few alternate presentations, for example, in the
Chemical Galaxy
.
[6]
3.
^
The noble gases, astatine, francium, and all elements heavier than americiumwere left out as there is no data for them.
4.
^
While fluorine is the most electronegative of the elements under the
Pauling scale
, neon is the most electronegative element under other scales, such as the
Allen scale
.
5.
^
While Lr is thought to have a p rather than d electron in its ground-state electron configuration, and would therefore be expected to be a volatile metal capable of forming a +1 cation in solution like thallium, no evidence of either of these properties has been able to be obtained despite experimental attempts to do so.
[64]
It was originally expected to have a d electron in its electron configuration[64] and this may still be the case for metallic lawrencium, whereas gas phase atomic lawrencium is very likely thought to have a p electron.
[65]
6.
^
An antecedent of Deming’s 18-column table may be seen in
Adams’ 16-column Periodic Table of 1911
. Adams omits the rare earths and the “radioactive elements” (i.e. the actinides) from the main body of his table and instead shows them as being “
careted
in only to save space” (rare earths between Ba and eka-Yt; radioactive elements between eka-Te and eka-I). See: Elliot Q. A. (1911). “A modification of the periodic table”. Journal of the American Chemical Society. 33(5): 684–688 (687).
7.
^
A second extra-long periodic table row, to accommodate known and undiscovered elements with an atomic weight greater than bismuth (thorium, protactinium and uranium, for example), had been postulated as far back as 1892. Most investigators considered that these elements were analogues of the third series
transition element
s, hafnium, tantalum and tungsten. The existence of a second inner transition series, in the form of the actinides, was not accepted until similarities with the electron structures of the lanthanides had been established. See: van Spronsen, J. W. (1969). The periodic system of chemical elements. Amsterdam: Elsevier. pp. 315–316,
ISBN
0-444-40776-6
.
8.
^
See
The Internet database of periodic tables
for depictions of these kinds of variants.
9.
^
The detachment of the lanthanides from the main body of the periodic table has been attributed to the Czech chemist
Bohuslav Brauner
who, in 1902, allocated all of them (“Ce etc.”) to one position in group 4, below zirconium. This arrangement was referred to as the “asteroid hypothesis”, in analogy to asteroids occupying a single orbit in the solar system. Before this time the lanthanides were generally (and unsuccessfully) placed throughout groups I to VIII of the older 8-column form of periodic table. Although predecessors of Brauner’s 1902 arrangement are recorded from as early as 1895, he is known to have referred to the “chemistry of asteroids” in an 1881 letter to Mendeleev. Other authors assigned all of the lanthanides to either group 3, groups 3 and 4, or groups 2, 3 and 4. In 1922
Niels Bohr
continued the detachment process by locating the lanthanides between the s- and d-blocks. In 1949 Glenn T. Seaborg (re)introduced the form of periodic table that is popular today, in which the lanthanides and actinides appear as footnotes. Seaborg first published his table in a classified report dated 1944. It was published again by him in 1945 in
Chemical and Engineering
News
, and in the years up to 1949 several authors commented on, and generally agreed with, Seaborg’s proposal. In that year he noted that the best method for presenting the actinides seemed to be by positioning them below, and as analogues of, the lanthanides. See: Thyssen P. and Binnemans K. (2011). “Accommodation of the Rare Earths in the Periodic Table: A Historical Analysis”. In K. A. Gschneider Jr. (ed). Handbook on the Physics and Chemistry of the Rare Earths. 41. Amsterdam: Elsevier, pp. 1–94; Seaborg G. T. (1994). Origin of the Actinide Concept’. In K. A. Gschneider Jr. (ed). Handbook on the Physics and Chemistry of the Rare Earths. 18. Amsterdam: Elsevier, pp. 1–27.
10.
^
For examples of this table see
Atkins
et al. (2006). Shriver & Atkins Inorganic Chemistry (4th ed.). Oxford: Oxford University Press • Myers et al. (2004). Holt Chemistry. Orlando: Holt, Rinehart & Winston •
Chang R.
(2000). Essential Chemistry (2nd ed.). Boston: McGraw-Hill
11.
^
For examples of the group 3 = Sc-Y-Lu-Lr table see Rayner-Canham G. & Overton T. (2013). Descriptive Inorganic Chemistry (6th ed.). New York: W. H. Freeman and Company • Brown et al. (2009). Chemistry: The Central Science (11th ed.). Upper Saddle River, New Jersey: Pearson Education • Moore et al. (1978). Chemistry. Tokyo: McGraw-Hill Kogakusha
12.
^
The phenomenon of different separation groups is caused by increasing basicity with increasing radius, and does not constitute a fundamental reason to show Lu, rather than La, below Y. Thus, among the Group 2 alkaline earth metals, Mg (less basic) belongs in the “soluble group” and Ca, Sr and Ba (more basic) occur in the “ammonium carbonate group”. Nevertheless, Mg, Ca, Sr and Ba are routinely collocated in Group 2 of the periodic table. See: Moeller et al. (1989). Chemistry with Inorganic Qualitative Analysis (3rd ed.). SanDiego: Harcourt Brace Jovanovich, pp. 955–956, 958.
13.
^
Notwithstanding, an IUPAC member subsequently wrote that, “IUPAC has not approved any specific form of the periodic table, and an IUPAC-approved form does not exist, though even members of IUPAC themselves have published diagrams titled “
IUPAC Periodic Table of the Elements
“. However, the only specific recommendation IUPAC has made concerning the periodic table covers the Group numbering of 1–18.”
[174]
14.
^
For examples of the group 3 = Ln and An table see Housecroft C. E. & Sharpe A. G. (2008). Inorganic Chemistry (3rd ed.). Harlow: Pearson Education • Halliday et al. (2005). Fundamentals of Physics (7th ed.). Hoboken, NewJersey: John Wiley & Sons • Nebergall et al. (1980). General Chemistry (6th ed.). Lexington: D. C. Heath and Company
15.
^
Karol (2002, p. 63) contends that gravitational effects would become significant when atomic numbers become astronomically large, thereby overcoming other super-massive nuclei instability phenomena, and that
neutron stars
(with atomic numbers on the order of 1021) can arguably be regarded as representing the heaviest known elements in the universe. See: Karol P. J. (2002). “The Mendeleev–Seaborg periodic table: Through Z = 1138 and beyond”. Journal of Chemical Education 79 (1): 60–63.
16.
^
Scerri, one of the foremost authorities on the history of the periodic table,
[196]
whilst previously recognising the value of a plurality of periodic tables,[195] currently supports the concept of an optimal table.
[197]
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. Oxford: Oxford University Press.
ISBN
978-0-19-530573-9
.
·
Scerri, E.
(2011). The periodic table: A very short introduction. Oxford: Oxford University Press.
ISBN
978-0-19-958249-5
.
·
Venable, F. P.
(1896).
The Development of the Periodic Law
. Easton, Pennsylvania: Chemical Publishing Company.
OCLC
776059614
.
Further reading
· Calvo, Miguel (2019). Construyendo la Tabla Periódica. Zaragoza, Spain: Prames. p. 407.
ISBN
978-84-8321-908-9
.
·
Emsley, J.
(2011). “The Periodic Table”. Nature’s Building Blocks: An A–Z Guide to the Elements (New ed.). Oxford: Oxford University Press. pp. 634–651.
ISBN
978-0-19-960563-7
.
· Fontani, Marco; Costa, Mariagrazia; Orna, Mary Virginia (2007). The Lost Elements: The Periodic Table’s Shadow Side. Oxford: Oxford University Press. p. 508.
ISBN
978-0-19-938334-4
.
·
Mazurs, E. G.
(1974). Graphical Representations of the Periodic System During One Hundred Years. Alabama: University of Alabama Press.
ISBN
978-0-19-960563-7
.
· Rouvray, D.H.; King, R. B., eds. (2004). The Periodic Table: Into the 21st Century. Proceedings of the 2nd International Conference on the Periodic Table, part 1, Kananaskis Guest Ranch, Alberta, 14–20 July 2003. Baldock, Hertfordshire: Research Studies Press.
ISBN
978-0-86380-292-8
.
· Rouvray, D.H.; King, R. B., eds. (2006). The Mathematics of the Periodic Table. Proceedings of the 2nd International Conference on the Periodic Table, part 2, Kananaskis Guest Ranch, Alberta, 14–20 July 2003. New York: Nova Science.
ISBN
978-1-59454-259-6
.
· Scerri, E (n.d.).
“Books on the Elements and the Periodic Table”
(PDF). Retrieved 9 July 2018.
· Scerri, E.; Restrepo, G, eds. (2018). Mendeleev to Oganesson: A Multidisciplinary Perspective on the Periodic Table. Proceedings of the 3rd International Conference on the Periodic Table, Cuzco, Peru 14–16 August 2012. Oxford: Oxford University Press.
ISBN
978-0-86380-292-8
.
· van Spronsen, J. W. (1969). The Periodic System of Chemical Elements: A History of the First Hundred Years. Amsterdam: Elsevier.
ISBN
978-0-444-40776-4
.
· Verde, M., ed. (1971). Atti del convegno Mendeleeviano: Periodicità e simmetrie nella struttura elementare della materia [Proceedings of the Mendeleevian conference: Periodicity and symmetry in the elementary structure of matter]. 1st International Conference on the Periodic Table, Torino-Roma, 15–21 September 1969. Torino: Accademia delle Scienze di Torino.
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Copper (Cu):
“Shiny, reddish copper was the first metal ever manipulated by humans, and it remains an important metal in industry today” (1).
Chemistry:
With an atomic number of 29, Copper (Cu) is a very unique looking metal by appearance. The exterior does hold a “red-orange metallic luster,” and copper is a “soft, malleable, and ductile metal” as well. Basically, as “a freshly exposed surface of pure copper has a reddish orange color” to it, the metal is also utilized as the pure driver to produce heat and electricity. Below is a picture of what copper looks like in its natural state.
To continue being factual, Copper’s atomic number, 29, represents the number of protons in the nucleus. Its atomic weight, which is the average mass of the atom, is 63.55 grams. It has a density of 8.92 grams per cubic centimeter, and clearly, as the picture indicates, copper is solid at room temperature. The pure metal melts at 1,984.32 degrees Fahrenheit and boils at 5,301 degrees Fahrenheit.
Before use, copper “must be smelted for purity,” and most often occurring is ores. De facto of Mother Nature, “natural chemical reactions do sometimes release native copper,” and this enlightens us why humans have been using copper “for at least 8,000 years” to make tools and creating new technologies. Increasing supplies with copper, “people figured out how to smelt copper by about 4500 B.C.” As advancements started happening, copper alloys were made, by adding tin, “people made a harder metal: bronze.”
An intriguing statistic says “about two-thirds of the copper on Earth is found in igneous (volcanic) rocks.” According to the USGS, roughly a quarter of copper is stated in sedimentary rocks. While it is a metal that carries characteristics of being ductile and malleable, this can also explain its use in electronics and wiring.
Copper is known to turn green sometimes; this is a result of an oxidation reaction. This means that it is losing elections when it is vulnerable to air and water. Like stated, “the resulting copper oxide is a dull green.” The reason the Statue of Liberty has a green appearance rather than a red-orange color is from the oxidation reaction that happened to the original copper. In
accordance with the Copper Development Association, “a weathered layer of copper oxide only 0.005 inches thick coats Lady Liberty (2).” Take a look below at oxidized copper (3), and an electron configuration for copper to get a more molecular idea (2).
Business:
Currently, copper is listed at $3.04/lb. and equivalently $6,702.93/t. Just trading over $3 a pound, the fine metal “is up close to 28 percent year-to-date and far outperforming its five-year average from 2012 to 2016.” There are many factors that are influencing the price of the metal as we speak. As represented by the purchasing manager’s index (PMI), manufacturing activity is growing at a rate that hasn’t been witnessed in years in the U.S., Eurozone, and China. September of 2017 marked the 100th straight month of expansion, conquering a 13-year high of 60.8. Reflect the graph below to see how copper outperformed its five-year average.
Another belief that is influencing the price of copper is the shortages that are happening in China; despite September 2017, “imports of the metal rising to its highest level since March” 2017. The world’s second-largest economy “took in 1.47 million metrics of copper ore and concentrates” in September 2017 as well, which is an amount that equates to six percent more than the same month in 2016.
Another reason so much copper is entering China is because of battery electric vehicles (BEVs); these demand “three to four times as much copper as traditional fossil fuel-powered vehicles.” While China has a tight and the most profitable grasp on the BEV market, according to the Financial Times, Beijing is working on putting a stop and ultimately prohibit the retailing of fossil fuel-powered vehicles. Nonetheless, just because of the vertical magnitude of the Chinese market, “this move is sure to delight copper bulls and investors in any metal that’s set to benefit from higher BEV production (4).” 54 percent of all new car transactions by 2040 will be BEVs, according to Bloomberg New Energy Finance. Expectedly, China, Europe, and the U.S. are accounted to make up 60 percent of the worldwide BEV fleet. With the rise in BEV automobiles, this predicts a huge effect on copper prices over the span of the next ten years and more. Take a look at the graph below that charts the driving demand for copper due to electric vehicles in the coming years.
Conclusion:
Since copper occurs directly in nature, this led to very early human use; “it was the first metal to be smelted from its ore, the first metal to be cast into a shape in a mold, and the first metal to be purposefully alloyed with another metal (2).” The characteristics of this metal made it so versatile for early humans to make tools and get jobs done. It is truly amazing how a metal like copper revolutionized technology for humans and brought so much innovation and opportunities.
As there is a current market for copper today, it is getting traded at just over $3 a pound, and it is used today in electronics and wiring. Also, copper is way outperforming its five-year average, and the need for copper in electric vehicles exponentially rises for the next ten years, continued to 2040. This means that the demand for copper is not slowing down, and if anything, the price will go up because the demand for the copper has gone up as well. Copper plays a vital and also low-key factor in our economy, and the green on your pennies symbolize the oxidization that has occurred over time to your copper penny.
Works Cited (Sources)
1.
https://www.livescience.com/29377-copper.html
2.
https://en.wikipedia.org/wiki/Copper
3.
4.
http://www.businessinsider.com/copper-is-the-metal-of-the-future-2017-10
Palladium (Pd):
The next best thing to gold, palladium, my precious. Unique like gold and platinum, palladium is a game changer in organic and organometallic chemistry.
Chemistry:
Palladium sits in the D-block (group 10) on the periodic table of elements and is identified by its atomic mass of 46. The physical appearance of the palladium metal is silvery-white and very appealing to the eye. In addition, it is a very rare metal that is often only mined in Russia and South Africa1. The palladium metal is primarily used in catalytic converters to convert harmful greenhouse gases to less harmful pollutants, but has other uses as well. The metal in its solid state is pictured below.
Palladium shares its unique value with other high value metals such as platinum, rhodium, ruthenium, iridium, and osmium1. These metals make the platinum group metals on the periodic table however, palladium has the lowest melting point (1554.9 °C) and lowest density (12.03 g/cm3) among them all1.The metal is solid at room temperature and boils at 2963 °C. A comparison of the metal among other metals in illustrated in the picture below.
Palladium has also found use in the study of organometallics. The element most widely used today in organic synthesis is palladium….there is a wide range of Pd coupling reactions available; Pd reactions are very tolerant of functionality and give predictable products2. This could be due to the fact that late metals are relatively electronegative, so they tend to retain their valence electrons. The low oxidation states, such as d8 Pd (II), tend to be stable, and the higher ones, such as d6 Pd (IV), often find ways to return to Pd (II); that is, they are oxidizing2.
Business:
As of today’s date, September 27, 2019, palladium is valued at $1,586.00 an ounce, while gold, now cheaper than palladium, is valued at $1,501.90 shown in Figure 33. A decade ago, palladium was valued at a cost less than $300 an ounce seen in Figure 2. The reason for the soaring price of palladium is due to an acute shortage, which has driven prices to a record; the supply isn’t meeting the demand4. Palladium is a key component in pollution-control devices for cars and trucks4. In addition to the car industries large demand for the precious metal, several governments such as Chinas are cracking down on pollution from vehicles forcing carmakers to increase the amount of palladium being used4. This is a no brainer considering the push to a cleaner environment to reduce our contribution to climate change.
Figure 2. The chart displays a price comparison between gold and palladium for the year 2008. During the month of September, Gold was valued at $877.80 whereas palladium was valued at $222.00.
Figure 3. The chart displays a price comparison between gold and palladium for the current year 2019. During the month of September, Gold was valued at $1501.90 whereas palladium was valued at $1586.00.
Conclusion:
Due to the fact that palladium is found alloyed with other metals such as gold and other platinum-group metals makes it very rare and expensive. A consequence of this has led to a plague of catalytic converters being stolen from cars to harvest the precious metals buried inside5. Further, businesses such as U-Haul and similar companies are being targeted because larger trucks provide not only easy access to the catalytic converter, but also a greater yield of palladium5. It’s a wise move from the thieves because larger vehicles would need more of the metal.
It is without a doubt that the market for palladium will only continue to grow. Palladium is currently being used for electrical contacts, and dental fillings and crowns5. In addition to the applications mentioned, palladium and gold are combined to form the alloy white gold which is primarily used for aesthetic purposes i.e. jewelry. In my opinion, I question whether the market for palladium will slow once the price reaches an absolute high. I also wonder if offsetting the use of palladium with other metals via subsidies would do any help to curve the demand for the metal. In addition, the recycling of the palladium metal should theoretically mean there is more of it in the market, but perhaps it is being applied to different applications than what it had originated from.
Works Cited
1. Palladium. (2019, September 23). Retrieved from
https://en.wikipedia.org/wiki/Palladium
.
1. Crabtree, R. (2019). Organometallic Chemistry Of The Transition Metals. S.l.: WILEY-BLACKWELL.
1. Live Palladium Price. (0AD). Retrieved from
https://www.kitco.com/charts/livepalladium.html
.
1. Rowling, R. (2018, December 20). Why Palladium’s Suddenly an Especially Precious Metal. Retrieved from https://www.bloomberg.com/news/articles/2018-12-21/why-palladium-s-suddenly-an-especially-precious-metal-quicktake.
1. Frost, N. (2019, January 29). Thieves are breaking into cars to steal a metal more valuable than gold. Retrieved from https://qz.com/1536731/thieves-are-breaking-into-u-hauls-to-steal-catalytic-converters-for-palladium/.