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Molybdenum cube and fragment.


From New Latin molybdaenum, from molybdaena (any of various substances resembling lead), from Ancient Greek μολύβδαινα (molúbdaina, a plummet, piece of lead), from μόλυβδος (mólubdos, lead; graphite), from an Anatolian word cognate with Lydian 𐤪𐤠𐤭𐤦𐤥𐤣𐤠 (mariwda, dark), from Proto-Indo-European *morkʷ-iyo-, from a root *morkʷ- (dark), cognate with English murk.[1] Cf. Latin plumbum nigrum, lead. The suffix is +‎ -um (a chemical element).

Attested since the last quarter of 18th century.


  • enPR: məlĭb'dĭnəm, IPA(key): /məˈlɪbdɪnəm/
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molybdenum (countable and uncountable, plural molybdenums)

  1. A chemical element (symbol Mo) with an atomic number of 42: a silvery metal, not found as a free element, used in steel alloys.
    • 1803, “Of Metals”, in George Gleig, editor, Supplement to the Third Edition of the Encyclopædia Britannica, or, A Dictionary of Arts, Sciences, and Miscellaneous Literature, 2nd edition, volume I, page 225:
      The metals at preſent amount to 21 ; only 11 of which were known before the year 1730. Their names are gold, ſilver, platinum, mercury, copper, iron, tin, lead, zinc, antimony, biſmuth, arſenic, cobalt, nickel, manganeſe, tungſten, molybdenum, uranium, tellurium, titanium, chromum.
    • 1928, Lawrence R. Bourne, chapter 4, in Well Tackled![1]:
      Technical terms like ferrite, perlite, graphite, and hardenite were bandied to and fro, and when Paget glibly brought out such a rare exotic as ferro-molybdenum, Benson forgot that he was a master ship-builder, […]
    • 1990, Arthur J. Conacher, “Salt of the Earth”, in Environment[2], volume 32, number 6, page 40:
      At pH levels below 5, wheat yields may be low, molybdenum may become unavailable to plants, and other trace elements may be concentrated to toxic levels.
  2. A single atom of this element.
    a quadruple bond between molybdenums
    • 2007, Peter Day, Molecules into Materials: Case Studies in Materials Chemistry—Mixed Valency, Magnetism and Superconductivity, page 233:
      Thus in M4O11, for example, ¾ of the molybdenums are octahedrally connected and ¼ are tetrahedrally coordinated and, furthermore, the formula is compatible with the existence of one Mo(IV) for every three Mo(VI), so at first glance the compound might appear to be a class I mixed valence system.

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  1. ^ Beekes, Etymological Dictionary of Greek