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Molybdenum


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Atomic Number:42Atomic Symbol:Mo
Atomic Weight:95.94Electron Configuration:2-8-18-13-1
Shells:2,8,18,13,1Filling Orbital:4d5
Melting Point:2617oCBoiling Point:4612oC
Uses:Used in aircrafts, missiles, protective coatings and also for filaments in electric heaters.

History

(Gr. molybdos, lead). Discovered by Carl Wilhelm Scheele of Sweden in 1778. Before Scheele recognized molybdenite as a distinct ore of a new element, it was confused with graphite and lead ore. The metal was prepared as an impure form in 1782 by Hjelm.

Sources

Molybdenum does not occure native, but is obtained principally from molybdenite. Wulfenite, and Powellite are also minor commercial ores. Molybdenum is also recovered as a by-product of copper and tungsten mining operations. The metal is prepared from the powder made by the hydrogen reduction of purified molybdic trioxide or ammonium molybdate.

Properties

The metal is silvery white, very hard, but is softer and more ductile than tungsten. It has a high elastic modulus, and only tungsten and tantalum, of the more readily available metals, have higher melting points. It is a valuable alloying agent, as it contributes to the hardenability and toughness of quenched and tempered steels. It also improves the strength of steel at high temperatures. It is used in certain nickel-based alloys, such as the "Hastelloys(R)" which are heat-resistant and corrosion-resistant to chemical solutions. Molybdenum oxidizes at elevated temperatures.

Uses

The metal has found recent application as electrodes for electrically heated glass furnaces and foreheaths. The metal is also used in nuclear energy applications and for missile and aircraft parts. Molybdenum is valuable as a catalyst in the refining of petroleum. It has found applications as a filament material in electronic and electrical applications. Molybdenum is an essential trace element in plant nutrition. Some lands are barren for lack of this element in the soil. Molybdenum sulfide is useful as a lubricant, especially at high temperatures where oils would decompose. Almost all ultra-high strength steels with minimum yield points up to 300,000 psi(lb/in.^2) contain molybdenum in amounts from 0.25 to 8%.

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