Promethium (Pm)

From Wikipedia, the free encyclopediaPromethium, 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.

Promethium in the periodic table

Atomic number61
Element categoryLanthanide

Physical properties

Phase at STPSolid
Density7.26 g/cm3
Atomic weight145 u
Melting point1315 K
1041.85 °C
1907.33 °F
Boiling point3273 K
2999.85 °C
5431.73 °F

Atomära egenskaper

Electronegativity (Pauling Scale)1.13
Electron affinity12.45 kJ/mol
Ionization energies
1540 kJ/mol
2 1050 kJ/mol
3 2150 kJ/mol
4 3970 kJ/mol

Electron configuration

Electron configuration1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f5 5s2 5p6 6s2
Electrons per shell2, 8, 18, 23, 8, 2


Discovered byChien Shiung Wu
Emilio Segrè
Hans Bethe
Named byIsotopes of promethium