praseodymium

praseodymium
/pray'zee oh dim"ee euhm, pray'see-/, n. Chem.
a rare-earth, metallic, trivalent element, named from its green salts. Symbol: Pr; at. wt.: 140.91; at. no.: 59; sp. gr.: 6.77 at 20°C.
[1880-85; < NL, equiv. to praseo- (comb. form repr. Gk prásios leek-green; see PRASE) + (DI)DYMIUM]

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 (Pr), chemical element, rare-earth metal of transition Group IIIb of the periodic table, used as the element in special alloys and, as its oxide, in glasses (glass). Moderately soft, ductile, and malleable, this silvery metal rapidly displaces hydrogen from water and slowly reacts in air, developing a green oxide coating, which chips. For preservation, the metal must be sealed in a plastic covering or kept in mineral oil. Praseodymium was discovered in didymia, a mixture of several rare-earth oxides. From it, by repeated fractional crystallization of ammonium didymium nitrate, Carl Auer von Welsbach (Welsbach, Carl Auer, Freiherr von) separated (1885) salts of the elements praseodymium (the green fraction) and neodymium. Praseodymium occurs in minerals such as monazite and bastnaesite and as one of the products of nuclear fission. Natural praseodymium is all stable isotope praseodymium-141. This element is commercially separated and purified by ion-exchange techniques; the reduction of the fluoride or chloride with calcium is one way in which the metal itself is prepared.

      Praseodymium is a minor constituent of the alloy misch metal, used to make flints for cigarette lighters, and of high-strength, low-creep magnesium alloys for jet-engine parts. An alloying agent consisting primarily of praseodymium and neodymium gives magnesium alloys still higher strengths at all temperatures. A mixture of praseodymium and neodymium is the active component in didymium glass, used for goggles to protect the eyes of glassblowers and welders. Praseodymium compounds are used also to produce the yellow colour of some ceramics and other glasses.

      This element forms trivalent compounds such as the olive-green oxide Pr2O3, which dissolves readily in acids to yield green trivalent praseodymium salts. The tetravalent blackish purple dioxide PrO2 is known, but the Pr4+ ion is unknown in aqueous solution.

atomic number
59
atomic weight
140.907
melting point
931° C
boiling point
3,212° C
specific gravity
6.772 (25° C)
valence
3
electronic config.
2-8-18-21-8-2 or (Xe)4f35d06s2

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Universalium. 2010.

См. также в других словарях:

  • Praseodymium — (pronEng|ˌpreɪzioʊˈdɪmiəm or IPA|/ˌpreɪsioʊˈdɪmiəm/) is a chemical element that has the symbol Pr and atomic number 59. Characteristics Praseodymium is a soft silvery metal in the lanthanide group. It is somewhat more resistant to corrosion in… …   Wikipedia

  • Praseodymium — Pra se*o*dym i*um, n. [Praseo + didymium.] (Chem.) An elementary substance, one of the constituents of didymium; so called from the green color of its salts. Symbol Ps. Atomic weight 143.6. [1913 Webster] …   The Collaborative International Dictionary of English

  • praseodymium — Symbol: Pr Atomic number: 59 Atomic weight: 140.907 Soft silvery metallic element, belongs to the lanthanoids. Only natural isotope is Pr 141 which is not radioactive. Fourteen radioactive isotopes have been artificially produced. Used in rare… …   Elements of periodic system

  • praseodymium — rare metallic element, 1885, coined in Modern Latin by discoverer Carl Auer von Welsbach (1858 1929) from Gk. prasios leek green (from prason leek ) + didymos double, the name given to an earth in 1840, so called because it was a twin to lanthana …   Etymology dictionary

  • praseodymium — [prā΄zē ō dim′ē əm, prā΄sēō dim′ē əm] n. [ModL < praseodymia, a rare earth (< Gr prasios: see PRASE) + ModL (di)dymium (see DIDYMIUM): so named (1885) by C. A. von Welsbach (1858 1929), Austrian chemist, from its spectroscopic line and from …   English World dictionary

  • praseodymium — prazeodimis statusas T sritis chemija apibrėžtis Cheminis elementas. simbolis( iai) Pr atitikmenys: lot. praseodymium angl. praseodymium rus. празеодим …   Chemijos terminų aiškinamasis žodynas

  • praseodymium — prazeodimis statusas T sritis fizika atitikmenys: angl. praseodymium vok. Praseodym, n rus. празеодим, m pranc. praséodyme, m …   Fizikos terminų žodynas

  • praseodymium — noun Etymology: New Latin, alteration of praseodidymium, irregular from Greek prasios, adjective + New Latin didymium didymium Date: 1885 a yellowish white metallic element of the rare earth group used especially in alloys and in the form of its… …   New Collegiate Dictionary

  • praseodymium — noun A metallic chemical element (symbol Pr) with an atomic number of 59. See Also: didymium, neodymium, praseolite …   Wiktionary

  • praseodymium — An element of the lanthanide or “rare earth” group; atomic no. 59, atomic wt. 140.90765. [G. prasios, leekgreen, fr. prason, a leek, + didymos, twin] * * * pra·seo·dym·i·um .prā zē ō dim ē əm, .prā sē n a yellowish white trivalent metallic… …   Medical dictionary


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