Atomic number 61
Promethium
Lanthanide
Quick facts
- Atomic mass
- 145.00
- Group
- —
- Period
- 6
- State (STP)
- solid
- Electronegativity
- 1.13
- Common ox. states
- +3
Properties
Electron configuration
[Xe] 4f⁵ 6s²
- Ionization energy
- 540.0 kJ/mol
- Electron affinity
- 50.0 kJ/mol
- Melting point
- 1315.00 K (1041.8 °C)
- Boiling point
- 3273.00 K (2999.8 °C)
How it bonds· family overview
Promethium (Pm) is a lanthanide — a soft, silvery metal that almost always loses 3 electrons to form a +3 ion (Ln³⁺). Its 4f electrons sit deep below the valence shell, so chemistry across the lanthanide row is remarkably similar: oxide, fluoride, chloride salts, all in the +3 state.