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Promethium

Metal radioactivesolid
Symbol: Pm
Atomic number: 61
Atomic mass: (144.9127)
Group: Lanthanide
CAS-number: 7440-12-2

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Physical data

Electronic dataThermal dataSteric data
Shells: 2, 8, 18, 23, 8, 2
Orbitals: [Xe] 4f5 6s2
Electronegativity: --, 1.1
1. Ionization potential: 5.55 eV
2. Ionization potential: 10.903 eV
3. Ionization potential: 22.283 eV
Oxidation states: 3
Electrical conductivity: --
Melting point: 1042 °C
Boiling point: 3000 °C (estimated)
Specific heat: 0.18 J/gK
Heat of fusion: -- kJ/mol
Heat of vaporization: -- kJ/mol
Thermal conductivity: 0.179 W/cmK
Atomic radius: 2.62 Å
Ionic radius: 1.09 Å (+3)
Covalent radius: 1.63 Å
Atomic volume: 22.39 cm³/mol
Density (293 K): 6.475 g/cm³
Crystal structure: hexagonal
hexagonal

Isotopes

NuclideAbundance [%]MassSpinHalflifeDecay modeDecay tree
143Pm 0 142.911 5/2 265y EC View
144Pm 0 144 5 360y EC View
145Pm 0 144.913 5/2 17.7y EC, α View
146Pm 0 146 3 5.53y EC, β- View
147Pm 0 146.915 7/2 2.62y β- View
148Pm 0 148 1 5.37d β- View
148Pmm 0 148 6 41.3d β-, IT View
149Pm 0 149 7/2 2.212d β- View
151Pm 0 151 5/2 1.183d β- View

Other info

Name origin:Named for the Greek god, Prometheus.
Description:Rare earth metal of synthetic origin on the earth, naturally made in stars.
Discovered by:J.A. Marinsky, L.E. Glendenin, C.D. Coryell
Year:1945
Place:United States
Sources:Does not occur naturally. Found among fission products of uranium, thorium, and plutonium.
Use(s):It has been used as a source of radioactivity for thickness-measuring gauges.