/preuh mee"thee euhm/, n. Chem.
a rare-earth, metallic, trivalent element. Symbol: Pm; at. no.: 61.
[1945-50; < NL; see PROMETHEUS, -IUM]

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 (Pm), chemical element, only rare-earth metal of transition Group IIIb of the periodic table not detected in nature. Conclusive chemical proof of the existence of promethium, the last of the rare-earth elements to be discovered, was obtained (1947) by J.A. Marinsky, L.E. Glendenin, and C.D. Coryell, who isolated the radioactive isotope promethium-147 (2.7-year half-life) from uranium fission products at the research site at Oak Ridge, Tenn. Identification was firmly established by spectroscopy. Earlier investigators thought that they had found the element with atomic number 61 in naturally occurring rare earths and had prematurely called it illinium and florentium. Promethium-147 is effectively separated from the other rare-earth fission products by an ion-exchange method. Its soft beta radiation is converted to electricity in miniature batteries formed by sandwiching promethium between wafers of a semiconductor such as silicon; these batteries operate in extreme temperatures for five years. Promethium has also been prepared by slow neutron bombardment of the isotope neodymium-146; the resultant isotope, neodymium-147, decays by electron emission to promethium-147. The metal itself was first prepared (1963) by reduction of the fluoride, PmF3, with lithium.

      All of the isotopes of promethium are unstable; the longest lived is promethium-145 (18-year half-life). Because of the short half-lives of its isotopes, any promethium that might result from spontaneous fission of uranium in uranium ores would occur in infinitesimal concentrations. The physical and chemical properties of promethium are those of a typical rare earth. It is trivalent in its compounds and solutions, most of which are pink or rose.

atomic number
stablest isotope
melting point
1,080° C
boiling point
2,460° C
specific gravity
electronic config.
2-8-18-23-8-2 or (Xe)4f55d06s2

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Universalium. 2010.

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  • Promethium — (pronEng|prəˈmiːθiəm/, /proʊˈmiːθiəm) is a chemical element with the symbol Pm and atomic number 61. It is notable for being the only other exclusively radioactive element besides technetium which is followed by chemical elements that have stable …   Wikipedia

  • Promethium — Prométhium Pour les articles homonymes, voir Pm. Prométhéum …   Wikipédia en Français

  • prométhium — [ prɔmetjɔm ] n. m. • promethium 1953; de Prométhée ♦ Chim. Élément atomique (Pm; no at. 61; m. at. [isotope de plus longue période] 145) du groupe des lanthanides. Tous les isotopes connus du prométhium sont radioactifs. prométhium n. m. CHIM… …   Encyclopédie Universelle

  • promethium — Symbol: Pm Atomic number: 61 Atomic weight: (147) Soft silvery metallic element, belongs to the lanthanoids. Pm 147, the only natural isotope, is radioactive and has a half life of 252 years. Eighteen radioisotopes have been produced, but all… …   Elements of periodic system

  • promethium — radioactive element, long one of the missing elements, 1948, so called by discoverers Jacob Marinsky and Lawrence Glendenin, who detected it in 1945 in the fusion products of uranium while working on the Manhattan Project. From PROMETHEUS (Cf.… …   Etymology dictionary

  • promethium — ☆ promethium [prō mē′thē əm ] n. [ModL: so named (1949) for earlier prometheum, name proposed by G. M. Coryell for element isolated (1948) by J. A. Marinsky & L. E. Glendenin, U.S. physicists < Gr Promētheus (see PROMETHEUS) in reference to… …   English World dictionary

  • Promethium — Eigenschaften …   Deutsch Wikipedia

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

  • Promethium — Pro|me|thi|um 〈n.; s; unz.; chem. 〉 zu den Metallen der Seltenen Erden gehörendes chem. Element, Ordnungszahl 61 [nach dem grch. Titanen Prometheus] * * * Pro|me|thi|um [nach der griech. Sagengestalt Prometheus; ↑ ium], das; s; Symbol: Pm;… …   Universal-Lexikon

  • Promethium — prometis statusas T sritis fizika atitikmenys: angl. cyclonium; illinium; promethium vok. Promethium, n rus. прометий, m pranc. prométheum, m; prométhium, m …   Fizikos terminų žodynas

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