| 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 | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Symbol | Pm | ||||||||
| Atomic number | 61 | ||||||||
| Group | 0 | ||||||||
| Period | 6 | ||||||||
| Block | f | ||||||||
| Element category | Lanthanide | ||||||||
Physical properties | |||||||||
| Phase at STP | Solid | ||||||||
| Density | 7.26 g/cm3 | ||||||||
| Atomic weight | 145 u | ||||||||
| Melting point | 1315 K 1041.85 °C 1907.33 °F | ||||||||
| Boiling point | 3273 K 2999.85 °C 5431.73 °F | ||||||||
Atomic properties | |||||||||
| Electronegativity (Pauling Scale) | 1.13 | ||||||||
| Electron affinity | 12.45 kJ/mol | ||||||||
| Oxidation states | +2, +3 (a mildly basic oxide) | ||||||||
| Ionization energies |
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Electron configuration | |||||||||
| Elektronkonfiguration (shorthand) | [Xe] 4f5 6s2 | ||||||||
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f5 5s2 5p6 6s2 | ||||||||
| Electrons per shell | 2, 8, 18, 23, 8, 2 | ||||||||
History | |||||||||
| Discovered | 1942 | ||||||||
| Discovered by | Chien Shiung Wu Emilio Segrè Hans Bethe | ||||||||
| Named by | Isotopes of promethium | ||||||||