Atomic number 27
Cobalt
Transition metal
Quick facts
- Atomic mass
- 58.933
- Group
- 9
- Period
- 4
- State (STP)
- solid
- Electronegativity
- 1.88
- Common ox. states
- +2, +3
Properties
Electron configuration
[Ar] 3d⁷ 4s²
- Ionization energy
- 760.4 kJ/mol
- Electron affinity
- 63.7 kJ/mol
- Melting point
- 1768.00 K (1494.8 °C)
- Boiling point
- 3200.00 K (2926.8 °C)
How it bonds
Cobalt usually shows +2, sometimes +3. Co²⁺ in water is pink; many cobalt(II) chloride compounds shift between pink and blue with humidity (the "humidity indicator" trick). Cobalt-60 is a common medical / industrial gamma source.