Promethium
Promethium, originally prometheum, is a chemical element with the symbol Pm and atomic number 61. All of its isotopes are radioactive; it is one of only two such elements that are followed in the periodic table by elements with stable forms, a distinction shared with technetium. Chemically, promethium is a lanthanide, which forms salts when combined with other elements.
A stylized shell model. Electrons are quantum objects, not particles following these literal paths. Sizes and motion are illustrative.
54 is the [Xe] core total across five shells.
At a glance
- Atomic number
- 61
- Atomic mass
- 145 u
- Phase
- Solid
- Density
- 7.26 g/cm³
- Melting point
- 1,315 K
- Boiling point
- 3,273 K
- First ionization energy
- 540 kJ/mol
- Electronegativity
- 1.13
- Electron affinity
- 12.45 kJ/mol
- Molar heat capacity
- Unavailable
- Period
- 6
- Appearance
- metallic
Conditions and isotopes affect measured properties. Some properties of short-lived elements are predicted. Electronegativity uses the Pauling scale.
Keep exploring
Explore the stories, imagery, and reference data in more depth. Properties with no value in the reference are marked unavailable.