Molybdenum. Chemical element, symbol Mo, with atomic number 42 and atomic weight 95.94; it is one of the transition elements. Metal gray it plated with a density of 2.10 g / cm3 (5907 oz / in3), melts at 2610ºC (4730ºF).
Summary
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- 1 General characteristics
- 2 Health effects
- 3 Environmental effects
- 4 Applications
- 5 Sources
General characteristics
Molybdenum is found in many parts of the world, but few deposits are rich enough to guarantee cost recovery. Most of the moly comes from mines where its recovery is the primary objective of the operation. The remainder is obtained as a by-product of certain copper processing operations .
Molybdenum forms compounds in which it has oxidation states, 0, 2+, 3+, 4+, 5+, 6+. It has not been observed as an ionizable cation, but cationic species such as molybdenyl are known. Molybdenum chemistry is extremely complex and, with the exception of halides and chalcogenides, very few simple compounds are known.
Molybdenum dioxide and trioxide are the most common and stable oxides; other oxides described are metastable and are essentially laboratory species.
Molybdic acid, H2MoO4 (or MoO3.H2O), forms a stable series of normal salts, of the type M22 + MoO4, M2 + MoO4 and M23 + (MoO4) 3. Polymeric molybdates or isopolymolybdates can be formed by acidifying a molybdate solution or, in some cases, by heating normal molybdates. Hydrogen peroxide reacts with various molybdates to form a series of peroxyanionic compounds.
Another group of molybdenum compounds are the heteropolyelectrolytes, by far a fundamental family of salts and free acids: each member contains a complex and high molecular weight anion. Molybdenum also forms halides and oxyhalogenides, which represent a wide range in stability and a series of oxide-like compounds homologous with S, Se, and Te.
Health effects
Based on animal experimentation, molybdenum and its compounds are highly toxic. Some evidence of hyperbilirubinemic liver dysfunction has been reported in workers chronically exposed to a Soviet copper moly plant . In addition, signs of gout have been found in factory workers and among the inhabitants of moly-rich areas of Armenia.
The main characteristics were joint pain in the knees, hands, feet, joint deformities, erythema, and edema of the joint areas.
Environmental effects
No negative effects of molybdenum on the environment have been documented.
Applications
Approximately two thirds of the molybdenum consumed is used in alloys. The use of molybdenum dates back to the First World War , when there was a strong demand for tungsten, which made it scarce, and very strong steels were needed. Molybdenum is thus used in high-strength alloys that withstand extremely high temperatures and corrosion. These alloys are used in construction and in aircraft and automobile parts. Molybdenum is used as a catalyst in the oil industry. In particular, it is useful for the removal of sulfur . 99Mo is used in the nuclear isotope industry. It is used in different pigments (with an orange color), for paints, dyes, plastics and rubber compounds.
The molybdenum disulfide (MoS2) is a good lubricant itself and provides tolerance properties of extreme pressure lubricants to react with the metal, so that a crystal layer is formed on the surface thereof. As a result, long-term destructive metal-to-metal contact is reduced to a minimum and can be used at high temperatures. Molybdenum is used in certain electronic applications, such as in conductive metal layers in TFT (Thin Film Transistor) transistors.
