Atomic number 61
Promethium
Lanthanide
In the real world
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 dangerous is it?
4/5 · Severe
The odd one out of this row: it is radioactive and has no stable form, so it is essentially absent from nature and made inside reactors. Worked with only in licensed labs.
- RadioactiveImmediate and cumulative
Every isotope of promethium decays and emits radiation; none is stable.
Handled only behind shielding by trained workers in licensed facilities.
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.
