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Element Fact
Iridium is the most corrosion-resistant metal known. Together with platinum, it is used to make the international prototype of the kilogram, which is the standard definition for the unit of mass.

Promethium, Pm

promethium sample

Atomic number: 61
Atomic mass: [145] (no stable nuclide)
Natural abundance: 10-20 ppm
143Pm (142.910928) - *
145Pm (144.912744) - *
147Pm (146.915134) - *

History and Production

From mythology Prometheus who stole fire from heaven. It was the first discovered in 1947 by J.A. Marinsky, L.E. Glendenin and C.D. Coryell who isolated the isotopes 147Pm from uranium fission products by ion-exchange chromatography at Oak Ridge. The isotope can also be prepared by neutron bombardment of the isotope 146Nd. It is used as a beta radiation source for electricity conversion in miniature batteries, useful for space probes and satellites which operate in extreme conditions.

Physical Data

The element is almost non-existence in nature, often associate with the natural uranium decays. The isotope with the longest half-life of about 18 years is 145Pm. Promethium salts luminesce in the dark with a greenish and pale blue glow.

Interatomic distance: 326 pm (covalent diameter)
Melting point: 1042C
Boiling point: 3000C (est.)
Thermal conductivity/Wm-1K-1: 17.9 (27C)
Density/kgm-3: 7220 (20C)

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: -
Gibbs free energy of formation: -
Entropy: 187.1 J/mol K
Heat capacity: 24.3 J/mol K

Electronic data

Electronic configuration: [Xe] 4f5 5s2
Term symbol: 6H5/2
Electron affinity: -   Electronegativity (Pauline): -
Ionization energy (first, second, third): 538.389, 1051.69, 2151.62 kJ/mol

Chemical properties

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