samarium

samarium , metallic chemical element; symbol Sm; at. no. 62; at. wt. 150.36; m.p. 1,072°C; b.p. 1,791°C; sp. gr. 7.54 at 20°C; valence +2 or +3. Samarium is a lustrous silver-white metal. It is one of the rare-earth metals of the lanthanide series in Group 3 of the periodic table . It has two crystalline forms (see allotropy ). The metal does not oxidize at room temperature but ignites when heated above 150°C. Samarium is found widely distributed in nature; it is obtained commercially from the minerals monazite and bastnasite. Naturally occurring samarium is a mixture of seven isotopes, three of which are radioactive with extremely long half-lives. The metal was not isolated in relatively pure form until recently, although it has long been used in pyrophoric alloys used in cigarette lighter flints. Samarium is used as a catalyst in certain organic reactions. A samarium-cobalt compound, SmCo ₅ , is used to make magnets for use in computer memories. The oxide, samaria, is used in special infrared absorbing glass and cores of carbon arc-lamp electrodes. Since one isotope of samarium is a good neutron absorber, the element has found use in nuclear reactor control rods. Samarium was discovered in 1879 by P. E. Lecoq de Boisbaudran by spectroscopic analysis of the mineral samarskite.

samarium (symbol Sm) Grey-white, metallic element of the lanthanide series (rare-earth metals). First identified spectroscopically in 1879 by French chemist Paul Lacoq de Boisbaudran (1838–1912), its chief ores are monazite and bastnasite. Samarium is used in carbon-arc lamps, as a neutron absorber in nuclear reactors, and as a catalyst. Some samarium alloys are used in making powerful permanent magnets. Properties: at.no. 62; r.a.m. 150.35; r.d 7.52; m.p. 1072°C (1962°F); b.p. 1791°C (3256°F); most common isotope Sm¹⁵² (26.72%).

sa·mar·i·um / səˈme(ə)rēəm/ • n. the chemical element of atomic number 62, a hard, silvery-white metal of the lanthanide series. (Symbol: Sm)