Iridium

Symbol: Ir
Atomic number: 77
Category: transition metals
Group: 9
Period: 6
Block: d
Atomic weight: 192.217 g/mol
Electrons per shell: 2, 8, 18, 32, 15, 2
CAS number: 7439-88-5
Phase: solid
Density: 22.56 kg/dm³ (near room temperature)
Melting point: 2739 K (2466 °C, 4471 °F)
Boiling point: 4701 K (4428 °C, 8002 °F)
Crystal structure: cubic face centered
Oxidation states: -3,-1, 0, 1, 2, 3, 4, 5, 6
Electronegativity: 2.20 (Pauling scale)
Name's origin: Iris
Name's meaning: the Greek winged goddess of the rainbow and the messenger of the Olympian gods, because many of the salts he obtained were strongly colored
Facts:
- a very hard, brittle, silvery-white transition metal of the platinum family
- is the second densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C
- is one of the rarest elements in the Earth's crust
- annual production and consumption is only three tonnes
- iridium compounds also find applications as catalysts for the production of acetic acid
- is used in spark plugs, crucibles for recrystallization of semiconductors at high temperatures, electrodes for the production of chlorine in the chloralkali process, and radioisotope thermoelectric generators used in unmanned spacecraft