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Platinum,  78Pt
General properties
Name, symbol Platinum, Pt
Appearance Silvery white metal
Platinum in the periodic table


Atomic number 78
Standard atomic weight (Ar) 195.084(9)
Group, block , d-block
Period period 6
Electron configuration [Xe] 4f14 5d9 6s1
per shell
2, 8, 18, 32, 17, 1
Physical properties
Phase Solid
Melting point 2041.4 K ​(1768.3 °C, ​3214.9 °F)
Boiling point 4098 K ​(3825 °C, ​​6917 °F)
Density near r.t. 21.45 g/cm3
when liquid, at  19.77 g/cm3
Heat of fusion 22.17 kJ/mol
Heat of 510 kJ/mol
Molar heat capacity 25.86 J/(mol·K)
Atomic properties
Oxidation states 6, 5, 4, 3, 2, 1, −1, −2, −3 ​ ​(a mildly basic oxide)
Electronegativity Pauling scale: 2.28
energies 1st: 870 kJ/mol
2nd: 1791 kJ/mol
Atomic radius empirical: 139 pm
Covalent radius 136±5 pm
Van der Waals radius 175 pm
Crystal structure ​Face-centered cubic (fcc)
Speed of sound thin rod 2800 m/s (at )
Thermal expansion 8.8 µm/(m·K) (at 25 °C)
Thermal conductivity 71.6 W/(m·K)
Electrical resistivity 1.05·10-7 Ω·m (at 20 °C)
Magnetic ordering Paramagnetic
Tensile strength 125–240 MPa
Young's modulus 168 GPa
Shear modulus 61 GPa
Bulk modulus 230 GPa
Poisson ratio 0.38
Mohs hardness 3.5
Vickers hardness 400–550 MPa
Brinell hardness 300–500 MPa
CAS Registry Number 7440-06-4
Discovery Antonio de Ulloa (1748)
· references

Platinum is a chemical element with the chemical symbol Pt and the atomic number 78. It is a valuable and useful transition metal, part of the so called "platinum group metals".



Platinum is extremely resistant to organic and mineral acids. It will, however, dissolve extremely slowly in hot aqua regia, to give chloroplatinic acid.

Pt + 4 HNO3 + 6 HCl → H2PtCl6 + 4 NO2 + 4 H2O

It will also be attacked by molten alkali and cyanides.


Platinum is a lustrous, ductile, and malleable, silver-white metal. It is more ductile than gold, but less malleable.


Although it can be bought from precious metal stores, platinum is also found in certain electronics and car exhaust catalysts. Electrodes are sometimes coated with platinum. Platinum can be obtained along with silver in small amounts from capacitors obtained through electronic recycling.

Platinum bullion can be bought, which has the advantage of having purity expressed accurately.

In Australia, platinum is classified as Category II precursor chemical and purchasing it requires and EUD.[1]


Platinum can be extracted by dissolving it in aqua regia. The resulting chloroplatinic acid is converted to ammonium chloroplatinate by the addition of ammonium chloride, that can be reduced to platinum metal by heating it, usually in a hydrogen atmosphere. This results in a platinum sponge.




Being a noble metal, it is non-toxic, though some of its compounds should be handled with care.


No special storage is required for storing platinum, though platinum electrodes should be kept away from sulfur oxides which can "poison" it.


It's best to recycle platinum, considering it's a rare and expensive metal.



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