Atomic number:77

Group numbers:9

Period:6

Electronic configuration:[Xe] 4f¹⁴ 5d⁷ 6s²

Formal oxidation number:+3 +4

Electronegativities:2.2

Atomic radius / pm:135.7

Relative atomic mass:192.217 ± 0.003

 

Iridium was discovered by Smithson Tennant (GB) in 1803. The origin of the name comes from the Latin word iris, meaning rainbow, because its salts are highly coloured. It is a heavy, brittle, white metal that is unreactive in air, water and acids but reacts with fused NaOH. Metal ignites and burns readily. Iridium is found in gravel deposits with platinum. It is used with osmium to tip gold pen points, to make crucible and special containers, also to make alloys used for standard weights and measures and heat-resistant alloys. It is used as a hardening agent for platinum.

Density / g dm^-3:22420 (290 K)

 20000 (m.p.)

Molar volume / cm³mol^-1:8.57 (290 K)

 8.74 (m.p.)

Electrical resistivity / μΩcm:5.3 (20 °C)

Thermal conductivity / W m^-1K^-1:147

Melting point / °C:2446

Boiling point / °C:4428

Heat of fusion / kJ mol^-1:26.4

Heat of vaporization / kJ mol^-1:612.1

Heat of atomization / kJ mol^-1:664.34

1st ionization energy / kJ mol^-1:865.19

2nd ionization energy / kJ mol^-1:-

3rd ionization energy / kJ mol^-1:-

in the atmosphere / ppm:-

in the Earth's crust / ppm:0.0001

in the oceans / ppm:-