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Element Fact
Selenium is an essential trace element in the diets that acts as antioxidants.

Samarium, Sm

samarium sample

Atomic number: 62
Atomic mass: 150.36(3)
Natural abundance: 7 ppm
147Sm (146.914893) - 15.0%
148Sm (147.914818) - 11.3%
149Sm (148.917180) - 13.8%
150Sm (149.917271) - 7.4%
152Sm (151.919728) - 26.7%
154Sm (153.922205) - 22.7%

History and Production

The name was derived from the mineral samarskite. It was isolated from samarskite and first identified by P.-E Lecoq de Boisbaudran in 1879 by spectroscopic means. The metal can be obtained commercially from monazite using ion-exchange and solvent extraction techniques. The metal is subsequently recovered by reduction of the oxide with lanthanum metal, follow by distillation of the metal. Misch metal contains about 1% of the element is used as lighting flints. With cobalt, it is used to make powerful magnet with the highest resistance to demagnetization of any known material. The metal is also used as a dopant to calcium fluoride crystals for use in laser and maser. It is also used in infrared-absrobing glass and as a neutron absorber in nuclear reactors.

Physical Data

Silvery-white in appearance and comparatively stable in air. It has a natural abundance of 7 ppm, often associate with other rare earth metals in monazite (mixture of phosphates) and bastnaesite (mixture of fluorocarbonate).

Interatomic distance: 324 pm (covalent diameter)
Melting point: 1074C
Boiling point: 1794C
Thermal conductivity/Wm-1K-1: 13.3 (27C)
Density/kgm-3: 7520 (20C)

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: 206.7 kJ/mol
Gibbs free energy of formation: 172.8 kJ/mol
Entropy: 183.0 J/mol K
Heat capacity: 30.4 J/mol K

Electronic data

Electronic configuration: [Xe] 4f6 5s2
Term symbol: 7F0
Electron affinity: -   Electronegativity (Pauline): 1.17
Ionization energy (first, second, third): 544.525, 1068.09, 2257.76 kJ/mol

Chemical properties

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