 Discovery Information
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| Who: Karl Wilhelm Scheele |
| When: 1778 |
| Where: Sweden |
|
| Name Origin
|
| Greek: molubdos (lead-like). |
| "Molybdenum" in different languages. |
|
| Sources
|
| Found in the minerals molybdenite (MoS2) and wulfenite (MoO4Pb) and as a byproduct of copper mining.
|
| Primary producers are the USA, Australia, Italy, Norway and Bolivia. Annual production is around 80 thousand tons. |
|
| Abundance
|
| Universe: 0.005 ppm (by weight) |
| Sun: 0.009 ppm (by weight) |
| Carbonaceous meteorite: 1.2 ppm |
| Earth's Crust: 1.5 ppm |
| Seawater: 0.01 ppm |
| Human: |
| 100 ppb by weight |
| 7 ppb by atoms |
|
| Uses
|
| In small quantities, molybdenum is effective at hardening steel. Used in aircraft, missiles, filaments in electric heaters
and protective coatings in boiler plates. Molybdenum oranges are pigments ranging from red-yellow to a bright red orange and
used in paints, inks, plastics, and rubber compounds.
|
| Molybdenum disulfide is a good lubricant, especially at high temperatures. Molybdenum is also used in some electronic applications,
as the conductive metal layers in thin-film transistors (TFTs).
|
|
| History
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| Molybdenite (MoS2)(from the Greek molybdos, meaning lead), the principal ore from which molybdenum is now extracted, was previously known as
molybdena. Molybdena was confused with and often implemented as though it were graphite. Even when the two ores were distinguishable,
molybdena was thought to be a lead ore. In 1754, Bengt Qvist examined the mineral and determined that it did not contain lead. It was not until 1778 that Swedish chemist Karl Wilhelm Scheele realized molybdena was neither graphite nor lead. He and other chemists then correctly assumed that it was the ore of a distinct new element, named molybdenum for the mineral
in which it was discovered. Peter Jacob Hjelm successfully isolated molybdenum using carbon and linseed oil in 1781.
|
| In World War I, some British tanks were protected by 75 mm manganese plating, but this proved to be ineffective. The manganese plates were then replaced with 25 mm molybdenum plating. These allowed for higher speed, greater manueverability and, despite
being thinner, better protection.
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|
| Notes
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| Over 66% of all molybdenum is used in alloys.
|
| Molybdenum has been found to have a role in the biology of all classes of organisms. It is found in two groups of enzymes,
the nitrogenases and the molybdopterins.
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|
| Hazards
|
| Molybdenum dusts and molybdenum compounds, such as molybdenum trioxide and water-soluble molybdates, may have slight toxicities if inhaled or ingested orally. Laboratory
tests suggest, compared to many heavy metals, that molybdenum is of relatively low toxicity. Acute toxicity in humans is unlikely
because the dose required would be exceptionally large.
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