|
Symbol
|
Pt
|
|
Atomic number
|
78
|
|
Atomic mass
|
195.09 g.mol -1
|
|
Electronegativity
according to Pauling
|
2.2
|
|
Density
|
21.4 g.cm-3 at 20°C
|
|
Melting point
|
1772 °C
|
|
Boiling point
|
3800 °C
|
|
Vanderwaals
radius
|
0.138 nm
|
|
Ionic radius
|
0.096 nm (+2)
|
|
Isotopes
|
13
|
|
Electronic
shell
|
[ Xe ] 4f14 5d9 6s1
|
|
Energy of
first ionisation
|
867 kJ.mol -1
|
|
Energy of
second ionisation
|
1788 kJ.mol -1
|
|
Discovered by
|
Julius Scaliger in 1735
|
Platinum
The name platinum is derived from the Spanish "platina",
meaning "little silver".
Platinum is a lustrous silvery-white, malleable, ductile metal and a
member of group 10 of the periodic table of the elements. It has the
third highest density, behind osmium
and iridium.
Platinum is unaffected by air and water, but will dissolve in hot aqua
regia, in hot concentrated phosphoric and sulphuric acids, and in molten
alkali. It is as resistant as gold to corrosion and tarnishing. Indeed,
platinum will not oxidize in air no matter how strongly it is heated.
It
has a coefficient of expansion almost equal to that of soda-lime-silica
glass, and is therefore used to make sealed electrodes in glass systems.
Hydrogen and oxygen gas mixtures explode in the presence of platinum wire.
There are six naturally occurring isotopes : the most abundant are
platinum-194, which accounts for 33%, platinum-195 (34%) and
platinum-196 (25%). The others are platinum-198 (7%), platinum-192 (1%)
and platinum-190 (0.01%). The latter is weakly radioactive, with a half
life of 700 billion years, while the other five are non-radioactive.
Applications
Platinum has many uses. Its wear- and tarnish-resistance
characteristics are well-suited for making fine jewelry. Platinum and
its alloys are used in surgical tools, laboratory utensils, electrical
resistance wires, and electrical contact points. It is used (30%) as a
catalyst in the catalytic converter, an optional component of the
gasoline-fuelled automobile exhaust system. The largest use (50%) of
platinum is for jewellery, another 20% is used in industry: platinum is
used in the chemical, electrical, glass and aircraft industries, each
accounting for about 10 tonnes of the metal per year. The glass industry
uses platinum for optical fibers and liquid crystal display glass,
especially for laptops.
Platinum in the environment
Platinum primary occurrence is with other metal ores associated with
basic igneous rocks. Platinum nuggets occur naturally as the uncombined
metal, as does an alloy of platinum-iridium. Three-quarters of the
world's platinum comes from South Africa, where it occurs as cooperite,
while Russia is the second largest produced, followed by North America.
World production of platinum is around 155 tonnes a year and reserves
total more than 30.000 tonnes
Back to
the periodic table of elements
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