My Saved Article
| Atomic Number: | 42 | Atomic Symbol: | Mo | | Atomic Weight: | 95.94 | Electron Configuration: | 2-8-18-13-1 | | Shells: | 2,8,18,13,1 | Filling Orbital: | 4d5 | | Melting Point: | 2617oC | Boiling 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.
SourcesMolybdenum 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.
PropertiesThe 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.
UsesThe 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%.
|
|
|