Molybdenum
MELTING POINT:
2,623°C
BOILING POINT:
4,639°C
DENSITY:
10.22 g/cm
3
MOST COMMON IONS:
Mo
3+
,
Mo
2
(OH)
2
4+
,
M
2
O
4
2+
Molybdenum is a hard, silver-white metal discovered by Swedish chemist Carl Wilhelm Scheele in 1778. Scheele had been researching a mineral called molybdenite, which many suspected of containing lead (the Greek word molybdos means "lead"). He instead found that it contained a new element which he named "molybdenum" after the mineral. Molybdenum was first isolated by Swedish mineralogist Peter Jacob Hjelm in 1782.
Molybdenum has an abundance in Earth's crust of approximately 1.1 parts per million (ppm) or 1.2 milligrams per kilogram. Its chief source is the mineral molybdenite (MoS 2 ), but it is also found in the ores wulfenite (PbMoO 4 ) and powellite (CaMoO 4 ) or obtained as a by-product of copper mining. The leading producers of molybdenum are the United States, Canada, Chile, Mexico, Peru, China, Russia, and Mongolia.
There are seven known isotopes of molybdenum that occur naturally: 92 Mo, 94 Mo, 95 Mo, 96 Mo, 97 Mo, 98 Mo, and 100 Mo. Their natural abundances range from 9.25 percent ( 94 Mo) to 24.13 percent ( 98 Mo). Common compounds of molybdenum include molybdenum disulfide (MoS 2 ), molybdenum trioxide (MoO 3 ), molybdic acid (H 2 MoO 4 ), molybdenum hexafluoride (MoF 6 ), and molybdenum phosphide (MoP 2 ).
Molybdenum's melting point (2,623°C, or 4,753.4°F) exceeds that of steel by 1,000°C (1,832°F) and that of most rocks by 500°C (932°F). For this reason, the element is used in various alloys to improve strength, particularly at high temperatures. Approximately 75 percent of molybdenum produced is used by the iron and steel industries. The element is also utilized to make parts for furnaces, light bulbs, missiles, aircraft, and guns. Molybdenum disulfide is used as a high temperature lubricant.
SEE ALSO Coordination Compounds ; Inorganic Chemistry ; Scheele, Carl .
Stephanie Dionne Sherk
Bibliography
Lide, David R., ed. (2003). The CRC Handbook of Chemistry and Physics, 84th edition. Boca Raton, FL: CRC Press.
Other Resource
Powell, Darryl. "Molybdenum." Mineral Information Institute. Available from http://www.mii.org/Minerals/photomoly.html .
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