(So named (Greek iris, "iris") in 1804 by S. Tennant, English chemist, because its salts have varied colors) A white, extremely dense, brittle, corrosion-resistant chemical element, one of the platinum metals. Alloys of iridium are used in electrodes, pen points, crucibles, etc.
Symbol: Ir
Atomic number: 77
Atomic weight: 192.217
Density (at
room temperature and
pressure): 22.4
g/
cc
Melting point: 2,410°
C
Boiling point: 4,430°
C
Valence: +3, +4
Ground state electron configuration: [
Xe]4f
145d
76s
2
Density at 300K: 22.6 g/cm
3
Covalent radius: 1.27
Atomic radius: 1.87
Atomic
volume: 8.54 cm
3/mol
First
ionization potental: 9.1 V
Specific heat capacity: 0.130 Jg
-1K
-1
Thermal conductivity: 147 Wm
-1K
-1
Electrical conductivity: 21.3*10
6Ω
-1m
-1
Heat of fusion: 26.36 kJ/mol
Heat of vaporization: 563.58 kJ/mol
Electronegativity: 2.20 (Pauling's)