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Iridium
Symbol: Ir
Atomic Number: 77
Atomic Weight: 192.22
Element Classification: Transition Metal
Discovered By: S.Tenant, A.F.Fourcory, L.N.Vauquelin, H.V.Collet-Descoltils
Discovery Date: 1804 (England/France)
Name Origin: Latin: iris (rainbow).
Density (g/cc): 22.42
Melting Point (°K): 2683
Boiling Point (°K): 4403
Appearance: White, brittle metal
Atomic Radius (pm): 136
Atomic Volume (cc/mol): 8.54
Covalent Radius (pm): 127
Ionic Radius: 68 (+4e)
Specific Heat (@20°C J/g mol): 0.133
Fusion Heat (kJ/mol): 27.61
Evaporation Heat (kJ/mol): 604
Thermal Conductivity (@25°C W/m K):
Debye Temperature (°K): 430.00
Pauling Negativity Number: 2.20
First Ionizing Energy (kJ/mol): 868.1
Oxidation States: 6, 4, 3, 2, 1, 0, -1
Electronic Configuration: [Xe] 4f14 5d7 6s2
Lattice Structure: Face-Centered Cubic (FCC)
Lattice Constant (Å): 3.840
Lattice C/A Ratio: n/a
Mineral Hardness [no units]: 6.5
Brinell Hardness [/MN m-2]: 1670
Vickers Hardness [/MN m-2]: 1760
Note: Iridium is much harder and more easily prepared than most precious metals. Relatively few metallographers work with precious
metals, other than those used in electronic devices.