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A silvery-white metallic element. Molybdenum occurs in the earth's crust in concentrations of 1-1.5 ppm. It is obtained from molybdenite and wulfenite ores and also as a by-product of Copper production. Molybdenum was first discovered by Carl William Scheele in 1778 and isolated by Peter Hjelm in 1782. Molybdenum is very resistant to corrosion, has high electrical conductivity and can withstand high temperatures. Metallic molybdenum is used in the manufacture of hardened steels, tools, boiler plate, rifle barrels, propeller shafts, x-ray tubes, electrical contacts, filaments, and glass-to-metal seals.

Synonyms and Related Terms

Mo; Molybdeen (Ned.); molybdène (Fr.); Molybdän (Deut.); molibdeno (It., Esp.); molibdénio (Port.); molybden (Sven.); molybdos (Gr.); molybdenite; wulfenite 




Physical and Chemical Properties

  • Flame color is green-yellow.
  • Insoluble in water, dilute hydrochloric acid and alkalis.
  • Reacts with nitric acid and sulfuric acid.
Composition Mo (atomic no. 42)
CAS 7439-98-7
Mohs Hardness 5.5
Melting Point 2622 C
Density 10.28 g/ml
Molecular Weight atomic wt = 95.94
Boiling Point 4639 C

Resources and Citations

  • Chemical & Engineering News, American Chemical Society, Washington DC, 81 (36) , Sept. 8, 2003 Comment: Philip Mitchell, p. 108; states discovered by Scheele in 1778
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 6317; discovered by Scheele in 1778 and isolated by Hjelm in 1782
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 516