Promethium

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Promethium is a chemical element with the symbol Pm and atomic number 61. It is notable for being the only other radioactive element besides technetium which is followed by chemical elements that have stable isotopes.

 

General
Name, Symbol, Number promethium, Pm, 61
Chemical series lanthanides
Group, Period, Block n/a, 6, f
Appearance metallic
Standard atomic weight [145](0) g·mol-1
Electrons per shell 2, 8, 18, 23, 8, 2
Physical properties
Phase solid
Density (near r.t.) 7.26 g·cm−3
Melting point 1315K
(1042°C, 1908°F)
Boiling point 3273K
(3000°C, 5432°F)
Heat of fusion 7.13 kJ·mol-1
Heat of vaporization 289 kJ·mol-1
Atomic properties
Crystal structure hexagonal
Oxidation states 3
(mildly basic oxide)
Electronegativity  ? 1.13 (Pauling scale)
Ionization energies
(more)
1st: 540 kJ·mol-1
2nd: 1050 kJ·mol-1
3rd: 2150 kJ·mol-1
Atomic radius 185 pm
Atomic radius (calc.) 205 pm
Miscellaneous
Magnetic ordering no data
Electrical resistivity (r.t.) est. 0.75 µΩ·m
Thermal conductivity (300K) 17.9 W·m-1·K-1
Thermal expansion (r.t.) (α, poly)
est. 11 µm/(m·K)
Young's modulus (α form) est. 46 GPa
Shear modulus (α form) est. 18 GPa
Bulk modulus (α form) est. 33 GPa
Poisson ratio (α form) est. 0.28
CAS registry number 7440-12-2

 

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