samarium

/seuh mair"ee euhm/, n. Chem.
a rare-earth metallic element discovered in samarskite. Symbol: Sm; at. wt.: 150.35; at. no.: 62; sp. gr.: 7.49.
[1875-80; < NL; see SAMARSKITE, -IUM]

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 (Sm), chemical element, rare-earth metal of the lanthanoid series of the periodic table. Samarium is silvery white in colour and is relatively stable in air. It was isolated as an impure oxide and spectroscopically identified as a new element (1879) by P.-É. Lecoq de Boisbaudran (Lecoq de Boisbaudran, Paul-Émile). Samarium occurs in many other rare-earth minerals but is almost exclusively obtained from monazite; (monazite) it is also found in the products of nuclear fission. Ion-exchange techniques are used for its commercial separation and purification. The metal is conveniently prepared by the thermoreduction of its oxide, Sm2O3, with lanthanum metal, followed by distillation of the samarium metal, which is one of the most volatile rare-earth elements. Several allotropes (structural forms) of samarium exist; at room temperature its structure is rhombohedral.

      Because of its high absorption cross section for thermal neutrons, samarium has been suggested for application in nuclear reactor control rods and for neutron shielding. Other uses are in special luminescent and infrared-absorbing glasses, in inorganic and organic catalysis, in magnetic alloys (combined with cobalt), and in the electronics and ceramics industries. Samarium is a minor constituent of misch metal (a mixture of cerium and other rare-earth metals, used in ferrous and nonferrous alloys).

      The seven naturally occurring isotopes of samarium are samarium-144 (3.1 percent), samarium-147 (15.0 percent), samarium-148 (11.3 percent), samarium-149 (13.8 percent), samarium-150 (7.4 percent), samarium-152 (26.7 percent), and samarium-154 (22.7 percent). Samarium-144, samarium-150, samarium-152, and samarium-154 are stable, but the other three naturally occurring isotopes are alpha emitters.

      In addition to its more stable +3 oxidation state, samarium, unlike most of the rare earths, has a +2 oxidation state. The Sm2+ ion is a powerful reducing agent that rapidly reacts with oxygen, water, or hydrogen ions. It can be stabilized by precipitation as the extremely insoluble sulfate SmSO4. Other salts of samarium in the +2 state are SmCO3, SmCl2, SmBr2, and Sm(OH)2; they are reddish brown in colour. In its +3 oxidation state samarium behaves as a typical rare-earth element; it forms a series of yellow salts in solutions.

atomic number
62
atomic weight
150.36
melting point
1,074° C
boiling point
1,794° C
density
7.520 g/cm3 (25° C)
oxidation states
+2, +3
electronic config.
[Xe]4f 65d06s2

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Universalium. 2010.

Look at other dictionaries:

  • samarium — [ samarjɔm ] n. m. • 1879; métal découvert dans la samarskite (minerai), du nom du chimiste russe Samarski ♦ Chim. Métal (Sm; no at. 62; m. at. 150,4) du groupe des lanthanides. Le samarium est utilisé pour absorber les neutrons dans les… …   Encyclopédie Universelle

  • Samarium — Sa*ma ri*um, n. [NL., fr. E. samarskite.] (Chem.) A rare metallic element of doubtful identity. [1913 Webster] Note: Samarium was discovered, by means of spectrum analysis, in certain minerals (samarskite, cerite, etc.), in which it is associated …   The Collaborative International Dictionary of English

  • samarium — Symbol: Sm Atomic number: 62 Atomic weight: 150.35 Soft silvery metallic element, belongs to the lanthanoids. Seven natural isotopes, Sm 147 is the only radioisotope, and has a half life of 2.5*10^11 years. Used for making special alloys needed… …   Elements of periodic system

  • Samarĭum — Sm (Sa), chemisch einfacher Körper, findet sich im Orthit und Thorit, Atomgewicht 150,3, bildet ein weißes Oxyd Sm2O3, das unschmelzbar ist, beim Glühen in Wasserstoff oder Sauerstoff sich nicht verändert, in Säuren sich leicht löst und gelbe,… …   Meyers Großes Konversations-Lexikon

  • Samarium — Samarium, Sa, ein im Orthit und Monazit sich findendes, zu den Edelerden gehörendes chemisches Element. Bujard …   Lexikon der gesamten Technik

  • Samarium — Samarĭum, sehr seltenes, wenig untersuchtes chem. Element, im Samarskit gefunden …   Kleines Konversations-Lexikon

  • samarium — [sə mer′ē əm, səmar′ē əm] n. [ModL: so named (1879) by Boisbaudran (see GALLIUM) < Fr samarskite (see SAMARSKITE), in which it occurs + IUM] a chemical element, one of the rare earth elements: symbol, Sm; at. no., 62: see the periodic table of …   English World dictionary

  • Samarium — promethium ← samarium → europium ↑ Sm ↓ …   Wikipedia

  • Samarium — Eigenschaften …   Deutsch Wikipedia

  • Samarium — Pour les articles homonymes, voir Sm. Samarium Prométhium ← Samarium → …   Wikipédia en Français

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