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 (@20C J/g mol): 0.133
Fusion Heat (kJ/mol): 27.61
Evaporation Heat (kJ/mol): 604
Thermal Conductivity (@25C 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 (): 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.

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