-- -- -- Nd Pm Sm U Np Pu Element Fact Rhenium was the last naturally occurring element to be identified, in 1925. It was so rare that only 1 g of the metal was extracted out of 660 kg of molybdenite ore.

Promethium, Pm Atomic number: 61 Atomic mass: [145] (no stable nuclide) Natural abundance: 10-20 ppm Isotopes: 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: 1042°C Boiling point: 3000°C (est.) Thermal conductivity/Wm-1K-1: 17.9 (27°C) Density/kgm-3: 7220 (20°C) 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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