uranium

uranium
A radioactive metallic element, atomic no. 92, atomic wt. 238.0289, occurring mainly in pitchblende and notable for its two isotopes: 238U and 235U (99.2745% and 0.720%, respectively, the rest being made up by 234U), 235U being the first substance ever shown capable of supporting a self-sustaining chain reaction. [G. myth. character, Uranus]

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ura·ni·um yu̇-'rā-nē-əm n a silvery heavy radioactive polyvalent metallic element that is found esp. in pitchblende and uraninite and exists naturally as a mixture of three isotopes of mass number 234, 235, and 238 in the proportions of 0.006 percent, 0.71 percent, and 99.28 percent respectively symbol U see ELEMENT (table)

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ura·ni·um (U) (u-raґne-əm) [L. Uranus a planet] a hard and heavy radioactive metallic element; atomic number, 92; atomic weight, 238.03; specific gravity, 18.68. Naturally occurring uranium is composed of three isotopes of mass numbers 234, 235, and 238. Uranium 235 separated from U 238 undergoes fission with slow neutrons, giving up neutrons which can join the nucleus of U 238 to form neptunium, which in turn decays by beta particle emission to form plutonium. Cf. neptunium and plutonium.

Medical dictionary. 2011.

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  • Uranium — (pronEng|jʊˈreɪniəm) is a silvery gray metallic chemical element in the actinide series of the periodic table that has the symbol U and atomic number 92. It has 92 protons and 92 electrons, 6 of them valence electrons. It can have between 141 and …   Wikipedia

  • Uranium — Protactinium ← Uranium → Neptunium Nd …   Wikipédia en Français

  • URANIUM — L’uranium (symbole U, numéro atomique 92) est un élément chimique métallique très dense (d = 19), dur, dont la couleur grise rappelle celle du nickel. Pendant les cent cinquante ans qui suivirent sa découverte, en 1789, par Martin Heinrich… …   Encyclopédie Universelle

  • uranium — [yoo rā′nē əm] n. [ModL: so named (1789) by M. H. Klaproth (see TELLURIUM), its discoverer, after URANUS, recently (1781) discovered planet + IUM] a very hard, heavy, silver colored, radioactive, metallic chemical element, one of the actinides,… …   English World dictionary

  • Uranium — U*ra ni*um, n. [NL., from Uranus the planet. See {Uranus}.] (Chem.) An element of the chromium group, found in certain rare minerals, as pitchblende, uranite, etc., and reduced as a heavy, hard, nickel white metal which is quite permanent. Its… …   The Collaborative International Dictionary of English

  • uranium — Symbol: U Atomic number: 92 Atomic weight: (231) White radioactive metallic element belonging to the actinoids. Three natural isotopes, U 238, U 235 and U 234. Uranium 235 is used as the fuel for nuclear reactors and weapons. Discovered by Martin …   Elements of periodic system

  • Uranium — Uranium, so v.w. Uranorama …   Pierer's Universal-Lexikon

  • Uranium — (U) Уран химический радиоактивный элемент (металл) с атомным номером 92 и атомной массой наиболее распространенного и устойчивого изотопа 238. Природный уран состоит из смеси трех изотопов урана 238, урана 235 и урана 234, из которых практическое …   Термины атомной энергетики

  • uranium — rare metallic element, 1797, named 1789 in Modern Latin by its discoverer, German chemist and mineralogist Martin Heinrich Klaproth (1743 1817), for the recently found planet URANUS (Cf. Uranus) (q.v.) …   Etymology dictionary

  • uranium — ► NOUN ▪ a grey dense radioactive metallic chemical element used as a fuel in nuclear reactors. ORIGIN from the planet Uranus …   English terms dictionary

  • uranium — /yoo ray nee euhm/, n. Chem. a white, lustrous, radioactive, metallic element, occurring in pitchblende, and having compounds that are used in photography and in coloring glass. The 235 isotope is used in atomic and hydrogen bombs and as a fuel… …   Universalium

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