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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

SymbolPm
Atomic number61
Group0
Period6
Blockf
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

Atomic properties

Electronegativity (Pauling Scale)1.13
Electron affinity12.45 kJ/mol
Oxidation states+2, +3
(a mildly basic oxide)
Ionization energies
1540 kJ/mol
2 1050 kJ/mol
3 2150 kJ/mol
4 3970 kJ/mol

Electron configuration

Elektronkonfiguration (shorthand)[Xe] 4f5 6s2
Electron configuration1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f5 5s2 5p6 6s2
Electrons per shell2, 8, 18, 23, 8, 2

History

Discovered1942
Discovered byChien Shiung Wu
Emilio Segrè
Hans Bethe
Named byIsotopes of promethium
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