Osmium - Os

Symbol: Os
Atomic Number: 76
Atomic Weight: 190.23
Element Classification: Transition Metal
Discovered By: Smithson Tenant
Discovery Date: 1804 (England)
Name Origin: Greek: osme (odor).

Density (g/cc): 22.57
Melting Point (°K): 3327
Boiling Point (°K): 5300
Appearance: Blue-white, lustrous, hard metal
Atomic Radius (pm): 135
Atomic Volume (cc/mol): 8.43
Covalent Radius (pm): 126
Ionic Radius: 69 (+6e) 88 (+4e)
Specific Heat (@20°C J/g mol): 0.131
Fusion Heat (kJ/mol): 31.7
Evaporation Heat (kJ/mol): 738
Thermal Conductivity (@25°C W/m K):
Debye Temperature (°K): n/a
Pauling Negativity Number: 2.2
First Ionizing Energy (kJ/mol): 819.8
Oxidation States: 8, 6, 4, 3, 2, 0, -2
Electronic Configuration: [Xe] 4f14 5d6 6s2
Lattice Structure: Hexagonal (HEX)
Lattice Constant (Å): 2.740
Lattice C/A Ratio: 1.579

Mineral Hardness [no units]: 7.0
Brinell Hardness [/MN m-2]: 3920

Note: Osmium is rarely encountered in its pure form; even its alloys are infrequent subjects for metallographers. Damaged surface layers are easily produced and grinding and polishing rates are low. It is quite difficult to prepare. Relatively few metallographers work with precious metals, other than those used in electronic devices.

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