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samarium |
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samarium (səmâr`ēəm), 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 rare-earth metals, in chemistry, group of metals including those of the lanthanide series and actinide series, usually yttrium, sometimes scandium and thorium, and rarely zirconium.
..... Click the link for more information. of the lanthanide series lanthanide series, a series of metallic elements, included in the rare-earth metals, in Group 3 of the periodic table. Members of the series are often called lanthanides, although lanthanum (atomic number 57) is not always considered a member of the series. ..... Click the link for more information. in Group 3 of the periodic table periodic table, chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley. In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table ..... Click the link for more information. . It has two crystalline forms (see allotropy allotropy [Gr.,=other form]. A chemical element is said to exhibit allotropy when it occurs in two or more forms in the same physical state; the forms are called allotropes. ..... Click the link for more information. ). 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 monazite , yellow to reddish-brown natural phosphate of the rare earths, mainly the cerium and lanthanum metals, usually with some thorium. Yttrium, calcium, iron, and silica are frequently present. ..... Click the link for more information. 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, SmCo5, 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 a silvery metallic element of the lanthanide series occurring chiefly in monazite and bastnaesite and used in carbon-arc lighting, as a doping agent in laser crystals, and as a neutron-absorber. Symbol: Sm; atomic no.: 62; atomic wt.: 150.36; valency: 2 or 3; relative density: 7.520; melting pt.: 1074°C; boiling pt.: 1794°C samarium [sə′mar·ē·əm] (chemistry) A rare-earth metal, atomic number 62, symbol Sm; melts at 1350°C, tarnishes in air, ignites at 200-400°C. Want to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit the webmaster's page for free fun content. |
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