Element 61
Promethium (Pm)
Promethium (Pm) is element 61 of the periodic table, a lanthanide in period 6 (f-block) with an atomic mass of 145 and is a solid at standard conditions.
At a glance
- Atomic number
- 61
- Symbol
- Pm
- Atomic mass
- 145 u
- Category
- Lanthanides
- Period
- 6
- Block
- f-block
- Phase at STP
- solid
Electron structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f5 5s2 5p6 6s2
- Shorthand configuration
- [Xe] 4f5 6s2
- Electrons per shell
- 2, 8, 18, 23, 8, 2
- Oxidation states
- +2, +3
Physical properties
- Melting point
- 1315 K
- Boiling point
- 3273 K
- Density
- 7.26 g/cm3
- Phase
- solid
Atomic properties
- Electronegativity (Pauling)
- 1.13
- Atomic radius
- 205 pm
- Covalent radius
- 199 pm
- First ionization energy
- 540 kJ/mol
- Electron affinity
- 50 kJ/mol
Notable isotopes
| Isotope | Mass | Abundance | Stability |
|---|---|---|---|
| Pm-145 | 144.91276 | — | Half-life 17.7 years |
Common uses
- Nuclear batteries
- Luminous paint
- Thickness gauges
Discovery
- Year
- 1945
- Discovered by
- Jacob A. Marinsky, Lawrence E. Glendenin, Charles D. Coryell
- Country
- USA