A lanthanoid element, the fifth element (cerium group) of the f-elements block, with the symbol Sm, atomic number 62, and atomic weight 150.36. Electron configuration [Xe] 4f66s2. Samarium is composed of stable (144Sm, 3.07%; 150Sm, 7.38%; 152Sm, 26.75%; 154Sm, 22.75%) and four radioactive (146Sm; 147Sm, 14.99%; 148Sm, 11.24%; 149Sm, 13.82% ) isotopes. Discovered by L. de Boisbaudran in 1879. Samarium exhibits oxidation states III and II; atomic radii 180 pm, covalent radii 199 pm; redox potential (acidic solution) Sm3+/Sm −2.414 V; Sm3+/Sm2+ −1.000 V; electronegativity (Pauling) 1.17. Ground electronic state of Sm3+ is 6H6/2 with S = 5/2, L = 5, J = 5/2 with λ = 240 cm−1. Most stable technogenic radionuclide 148Sm (half-life 7 × 1015 years). The most common compounds: Sm2O3, SmF3 and SmCl3. Biologically, samarium is of high toxicity, and LD50 is less than 50 mg of Sm2O3 for animals to cause respiratory stoppage immediately (Atkins et al. 2006; Cotton et al. 1999; Huheey et...
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