Molybdenum Information
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Molybdenum Element
Molybdenum is a chemical
element with the symbol Mo and atomic number 42. The name is from Neo-Latin
molybdaenum, from Ancient Greek Μόλυβδος molybdos, meaning lead, since its ores
were confused with lead ores.[6] Molybdenum minerals have been known throughout
history, but the element was discovered (in the sense of differentiating it as
a new entity from the mineral salts of other metals) in 1778 by Carl Wilhelm
Scheele. The metal was first isolated in 1781 by Peter Jacob Hjelm.[7]
Molybdenum does not occur
naturally as a free metal on Earth; it is found only in various oxidation
states in minerals. The free element, a silvery metal with a gray cast, has the
sixth-highest melting point of any element. It readily forms hard, stable
carbides in alloys, and for this reason most of world production of the element
(about 80%) is used in steel alloys, including high-strength alloys and
superalloys.
Most molybdenum compounds have
low solubility in water, but when molybdenum-bearing minerals contact oxygen
and water, the resulting molybdate ion MoO2−
4 is quite soluble.
Industrially, molybdenum compounds (about 14% of world production of the
element) are used in high-pressure and high-temperature applications as
pigments and catalysts.
he soft black mineral
molybdenite (molybdenum sulfide) was often mistaken for graphite or lead ore
until 1778 when an analysis by German chemist Carl Scheele revealed it was
neither one of these substances, and was in fact, a totally new element. But
since Scheele did not have a suitable furnace to reduce the white solid to
metal, it would still be a few years before the element was actually
identified, according to Chemicool. In fact, Scheele later became known as
"hard luck Scheele" because he made a number of chemical discoveries
— including oxygen — but the credit was always given to someone else.
Molybdenum-bearing enzymes are
by far the most common bacterial catalysts for breaking the chemical bond in
atmospheric molecular nitrogen in the process of biological nitrogen fixation.
At least 50 molybdenum enzymes are now known in bacteria, plants, and animals,
although only bacterial and cyanobacterial enzymes are involved in nitrogen
fixation. These nitrogenases contain molybdenum in a form different from other
molybdenum enzymes, which all contain fully oxidized molybdenum in a molybdenum
cofactor. These various molybdenum cofactor enzymes are vital to the organisms,
and molybdenum is an essential element for life in all higher eukaryote
organisms, though not in all bacteria.
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