Editorial Feature

Platinum Group Metals - Comparison of Physical Properties

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Platinum was introduced in Europe around 1750. Even before the arrival of Columbus, platinum was well-known to native South Americans.

Platinum belongs to the platinum group of metals and it is malleable, lustrous, and ductile. It occurs abundantly on the earth’s crust, with around 0.001 ppm.

Platinum is the most significant of the group of six metals (Pt, Os, Pd, Ru, Rh, and Ir). It does not react with water and oxygen and dissolves only in aqua regia or fused alkalis.


Platinum has several applications, for example, it is used to make weights and measure standards. It is employed to make electrodes that could be exposed to chemical attack and is applied in the electronics industry to make electrical contacts, which would be subjected to high temperatures.

At present, platinum is mainly used in car exhaust catalysts; where the platinum coating is applied on a ceramic honeycomb. It is also used in jewelry making like gold and silver, which has its own hallmark.

Physical and Mechanical Properties

The following table shows the mechanical and physical properties of the platinum group of metals in the Periodic Table of Elements.

  Platinum Iridium Osmium Palladium Rhodium Ruthenium Gold Silver
Chemical Symbols Pt Ir Os Pd Rh Ru Au Ag
Atomic Number 78 77 76 46 45 44 79 47
Atomic Weight 195.09 192.22 190.2 106.4 102.9055 101.07 196.967 107.87
Density g/cm3 21.45 22.65 22.61 12.02 12.41 12.45 19.3 10.5
Melting Point C 1769 2443 3050 1554 1960 2310 1064.43 961.93
Vickers Hardness (annealed) 41 220 -- 41 101 -- 20 26
Electrical Resistivity at 0 C microohm.cm 9.85 4.71 8.12 9.93 4.33 6.80 2.4 1.6
Thermal Conductivity Watts/meter/C 73 148 87 76 150 105 293 419
Tensile Strength (annealed) tons per square inch 9 71 -- 11 45 36 7 9

*FCC - face-centred cubic, HCP - hexagonal close-packed


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