Cobalt - Co

Symbol: Co
Atomic Number: 27
Atomic Weight: 58.9332
Element Classification: Transition Metal
Discovered By: George Brandt
Discovery Date: 1739 (Sweden)
Name Origin: German: kobold (goblin).

Density (g/cc): 8.9
Melting Point (°K): 1768
Boiling Point (°K): 3143
Appearance: Hard, ductile, lustrous bluish-gray metal
Atomic Radius (pm): 125
Atomic Volume (cc/mol): 6.7
Covalent Radius (pm): 116
Ionic Radius: 63 (+3e) 72 (+2e)
Specific Heat (@20°C J/g mol): 0.456
Fusion Heat (kJ/mol): 15.48
Evaporation Heat (kJ/mol): 389.1
Thermal Conductivity (@25°C W/m K):
Debye Temperature (°K): 385.00
Pauling Negativity Number: 1.88
First Ionizing Energy (kJ/mol): 758.1
Oxidation States: 3, 2, 0, -1
Electronic Configuration: [Ar] 3d7 4s2
Lattice Structure: Hexagonal (HEX)
Lattice Constant (Å): 2.510
Lattice C/A Ratio: n/a

Mineral Hardness [no units]: 5.0
Brinell Hardness [/MN m-2]: 700
Vickers Hardness [/MN m-2]: 1043

Note: Cobalt and its alloys are more difficult to prepare than nickel and its alloys. Cobalt is a tough metal with a hexagonal close-packed crystal structure and is sensitive to deformation damage by mechanical twinning. Grinding and polishing rates are lower for Co than for Ni, Cu or Fe. Preparation of cobalt and its alloys is somewhat similar to that of refractory metals. Despite its hcp crystal structure, crossed polraized light is not very useful for examining cobalt alloys compared to other hcp metals and alloys.

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