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molybdenum |
3 definitions found From Webster's Revised Unabridged Dictionary (1913) [web1913]: Molybdenum \Mol`yb*de"num\, n. [NL.: cf F. molybd[`e]ne. See {Molybdena}.] (Chem.) A rare element of the chromium group occurring in nature in the minerals molybdenite and wulfenite, and when reduced obtained as a hard, silver-white, difficulty fusible metal. Symbol Mo Atomic weight 95.9. From WordNet r 1.6 [wn]: molybdenum n : a polyvalent metallic element that resembles chromium and tungsten in its properties; used to strengthen and harden steel [syn: {Mo}, {atomic number 42}] From Elements database 20001107 [elements]: molybdenum Symbol: Mo Atomic number: 42 Atomic weight: 95.94 Silvery-white, hard metallic transition element. It is chemically unreactive and is not affected by most acids. It oxidizes at high temperatures. There are seven natural isotopes, and four radioisotopes, Mo-93 being the most stable with a half-life of 3500 years. Molybdenum is used in almost all high-strength steels, it has nuclear applications, and is a catalyst in petroleum refining. Discovered in 1778 by Carl Welhelm Scheele of Sweden. Impure metal was prepared in 1782 by Peter Jacob Hjelm. The name comes from the Greek word molybdos which means lead. Trace amounts of molybdenum are required for all known forms of life. All molybdenum compounds should be considered highly toxic, and will also cause severe birth defects.
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