Manganese




Manganese

MELTING POINT: 1,246 ±3°C
BOILING POINT: 2,061°C
DENSITY: 7.21–7.44 g/cm 3
, depending upon allotrope
MOST COMMON IONS: Mn 2+
, Mn 3+ , MnO 4 3− , MnO 4 2− , MnO 4

Manganese is a hard, brittle, gray-white metal in group 7B of the Periodic Table. It was recognized as an element in 1774 by Swedish chemist Carl Wilhelm Scheele and isolated by his assistant Johan Gottlieb Gahn later that year. The element's name is derived from the Latin word magnes , meaning "magnet." This refers to the magnetic property of the common ore pyrolusite.

Manganese is the twelfth most abundant transition element (1,060 parts per million of Earth's crust) with twenty-three known isotopes . Large nodules of manganese ore have been discovered on the ocean floor. The pure metal can be obtained by reduction of the oxide with sodium or by electrolysis.

Manganese is more reactive that any of its neighbors on the Periodic Table. It reacts with water to produce hydrogen gas and dissolves in dilute acids to form Mn 2+ . The most stable oxidation state of manganese is +2. The most important oxide formed is MnO 2 , which decomposes to Mn 2 O 3 if heated above 530°C (932°F). The deep-purple manganate (VII) salts (permanganates) are prepared in aqueous solution by oxidation of Mn 2+ .

Manganese metal is used in many alloys . In conjunction with aluminum and copper it forms strong ferromagnetic alloys. Ninety-five percent of all manganese ores are used in the production of steel. The element improves the strength and toughness of steel by acting as a scavenger of sulfur, preventing the formation of FeS, which induces brittleness. Biologically, manganese is an important trace element ; it is essential to the utilization of vitamin B 1 . Pyrolusite has been used in glassmaking since ancient Egypt, while MnO 2 is used in the manufacture of dry cells. The permanganate ion is a strong oxidizing agent and is used in quantitative analysis and medicine.

SEE ALSO Coordination Compounds ; Inorganic Chemistry ; Scheele, Carl .

Catherine H. Banks

Bibliography

Greenwood, Norman N., and Earnshaw, A. (1997). Chemistry of the Elements, 2nd edition. Boston: Butterworth-Heinemann.

Lide, David R., ed. (2003). "Manganese." In The CRC Handbook of Chemistry and Physics , 84th edition. Boca Raton, FL: CRC Press.

Internet Resources

"Manganese." U.S. Geological Survey, Mineral Commodity Summaries. Updated January 2003. Available from http://minerals.usgs.gov/minerals/pubs/commodity/manganese/420303.pdf .



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