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Molybdenum is a chemical element; it has symbol Mo and atomic number 42. The name is derived from Ancient Greek μόλυβδος , meaning lead, since its ores were sometimes confused with those of lead. (1994). 9780849304743, Chemical Rubber Publishing Company. ISBN 9780849304743 Molybdenum minerals have been known throughout history, but the element was discovered (in the sense of differentiating it as a new entity from the mineral salts of other metals) in 1778 by Carl Wilhelm Scheele. The metal was first isolated in 1781 by Peter Jacob Hjelm.
Molybdenum does not occur naturally as a Native metal on Earth; in its minerals, it is found only in oxidation state. The free element, a silvery metal with a grey cast, has the sixth-highest melting point of any element. It readily forms hard, stable in , and for this reason most of the world production of the element (about 80%) is used in steel alloys, including high-strength alloys and .
Most molybdenum compounds have low solubility in water. Heating molybdenum-bearing minerals under oxygen and water affords molybdate ion , which forms quite soluble salts. Industrially, molybdenum compounds (about 14% of world production of the element) are used as and Catalysis.
are by far the most common bacterial catalysts for breaking the [[chemical bond]] in atmospheric molecular [[nitrogen]] in the process of biological nitrogen fixation. At least 50 molybdenum enzymes are now known in bacteria, plants, and animals, although only bacterial and cyanobacterial enzymes are involved in nitrogen fixation. Most [[nitrogenase]]s contain an iron–molybdenum cofactor [[FeMoco]], which is believed to contain either Mo(III) or Mo(IV). By contrast Mo(VI) and Mo(IV) are complexed with [[molybdopterin]] in all other molybdenum-bearing enzymes. Molybdenum is an essential element for all higher [[eukaryote]] organisms, including humans. A species of [[sponge]], ''[[Theonella conica|Theonellidae]]'', is known for hyperaccumulation of molybdenum.
Gaseous molybdenum consists of the diatomic species Mo2. That molecule is a singlet state, with two unpaired electrons in bonding orbitals, in addition to 5 conventional bonds. The result is a sextuple bond.
All the synthetic isotopes of molybdenum decay into isotopes of niobium, technetium, or zirconium. The most stable of them is 93Mo, with a half-life of 4,839 years to electron capture, giving stable niobium.
The most common isotopic molybdenum application involves molybdenum-99, which is a fission product. It is a parent radioisotope to the short-lived gamma-emitting daughter radioisotope technetium-99m, a nuclear isomer used in various imaging applications in medicine.
From the perspective of commerce, the most important compounds are molybdenum disulfide () and molybdenum trioxide (). The black disulfide is the main mineral. It is roasted in air to give the trioxide:
The trioxide, which is volatile at high temperatures, is the precursor to virtually all other Mo compounds as well as alloys. Molybdenum has several , the most stable being +4 and +6 (bolded in the table at left).
Molybdenum(VI) oxide is soluble in strong alkaline water, forming molybdates (MoO42−). Molybdates are weaker oxidants than chromates. They tend to form structurally complex by condensation at lower pH values, such as Mo7O246− and Mo8O264−. Polymolybdates can incorporate other ions, forming . The dark-blue phosphorus-containing heteropolymolybdate PMo12O403− is used for the spectroscopic detection of phosphorus.
The broad range of of molybdenum is reflected in various molybdenum chlorides:
The accessibility of these oxidation states depends quite strongly on the halide counterion: although molybdenum(VI) fluoride is stable, molybdenum does not form a stable hexachloride, pentabromide, or tetraiodide.
Like chromium and some other transition metals, molybdenum forms , such as in Mo2(CH3COO)4 and Mo2Cl84−. (2025). 9781118744994, John Wiley & Sons. ISBN 9781118744994 The ECW model properties of the butyrate and perfluorobutyrate dimers, ECW model and Rh2(O2CR) 4, have been reported.
The oxidation state 0 and lower are possible with carbon monoxide as ligand, such as in molybdenum hexacarbonyl, Mo(CO)6.
Although (reportedly) molybdenum was deliberately alloyed with steel in one 14th-century Japanese sword (mfd. ), that art was never employed widely and was later lost. In the West in 1754, Bengt Andersson Qvist examined a sample of molybdenite and determined that it did not contain lead and thus was not galena.
By 1778 Sweden chemist Carl Wilhelm Scheele stated firmly that molybdena was (indeed) neither galena nor graphite. Instead, Scheele correctly proposed that molybdena was an ore of a distinct new element, named molybdenum for the mineral in which it resided, and from which it might be isolated. Peter Jacob Hjelm successfully isolated molybdenum using carbon and linseed oil in 1781.
For the next century, molybdenum had no industrial use. It was relatively scarce, the pure metal was difficult to extract, and the necessary techniques of metallurgy were immature. (1992). 9780849347580, CRC Press. ISBN 9780849347580 Early molybdenum steel alloys showed great promise of increased hardness, but efforts to manufacture the alloys on a large scale were hampered with inconsistent results, a tendency toward brittleness, and recrystallization. In 1906, William D. Coolidge filed a patent for rendering molybdenum Ductility, leading to applications as a heating element for high-temperature furnaces and as a support for tungsten-filament light bulbs; oxide formation and degradation require that molybdenum be physically sealed or held in an inert gas. In 1913, Frank E. Elmore developed a froth flotation process to recover molybdenite from ores; flotation remains the primary isolation process.
During World War I, demand for molybdenum spiked; it was used both in Vehicle armor and as a substitute for tungsten in . Some British tanks were protected by 75 mm (3 in) mangalloy plating, but this proved to be ineffective. The manganese steel plates were replaced with much lighter molybdenum steel plates allowing for higher speed, greater maneuverability, and better protection. The Germans also used molybdenum-doped steel for heavy artillery, like in the super-heavy howitzer Big Bertha, Chemical properties of molibdenum – Health effects of molybdenum – Environmental effects of molybdenum . lenntech.com because traditional steel melts at the temperatures produced by the propellant of the ton shell. After the war, demand plummeted until metallurgical advances allowed extensive development of peacetime applications. In World War II, molybdenum again saw strategic importance as a substitute for tungsten in steel alloys.
The world's production of molybdenum was 250,000 tonnes in 2011, the largest producers being China (94,000 t), the United States (64,000 t), Chile (38,000 t), Peru (18,000 t) and Mexico (12,000 t). The total reserves are estimated at 10 million tonnes, and are mostly concentrated in China (4.3 Mt), the US (2.7 Mt) and Chile (1.2 Mt). By continent, 93% of world molybdenum production is about evenly shared between North America, South America (mainly in Chile), and China. Europe and the rest of Asia (mostly Armenia, Russia, Iran and Mongolia) produce the remainder.
In molybdenite processing, the ore is first roasted in air at a temperature of . The process gives gaseous sulfur dioxide and the molybdenum(VI) oxide:
The resulting oxide is then usually extracted with aqueous ammonia to give ammonium molybdate:
Metallic molybdenum is produced by reduction of the oxide with hydrogen:
The molybdenum for steel production is reduced by the aluminothermic reaction with addition of iron to produce ferromolybdenum. A common form of ferromolybdenum contains 60% molybdenum.
Molybdenum had a value of approximately $30,000 per tonne as of August 2009. It maintained a price at or near $10,000 per tonne from 1997 through 2003, and reached a peak of $103,000 per tonne in June 2005. In 2008, the London Metal Exchange announced that molybdenum would be traded as a commodity.
Molybdenum can withstand extreme temperatures without significantly expanding or softening, making it useful in environments of intense heat, including military armor, aircraft parts, electrical contacts, industrial motors, and supports for filaments in light bulbs.
Most high-strength steel (for example, 41xx steels) contain 0.25% to 8% molybdenum. Even in these small portions, more than 43,000 tonnes of molybdenum are used each year in , , cast irons, and high-temperature .
Molybdenum is also used in steel alloys for its high corrosion resistance and weldability. Molybdenum contributes corrosion resistance to type-300 stainless steels (specifically type-316) and especially so in the so-called
/ref> and martensitic (for example 1.4122 and 1.4418) stainless steels.
Because of its lower density and more stable price, molybdenum is sometimes used in place of tungsten. An example is the 'M' series of high-speed steels such as M2, M4 and M42 as substitution for the 'T' steel series, which contain tungsten. Molybdenum can also be used as a flame-resistant coating for other metals. Although its melting point is , molybdenum rapidly oxidizes at temperatures above making it better-suited for use in vacuum environments.
TZM (Mo (~99%), Ti (~0.5%), Zr (~0.08%) and some C) is a corrosion-resisting molybdenum superalloy that resists molten fluoride salts at temperatures above . It has about twice the strength of pure Mo, and is more ductile and more weldable, yet in tests it resisted corrosion of a standard eutectic salt (FLiBe) and salt vapors used in molten salt reactors for 1100 hours with so little corrosion that it was difficult to measure. Due to its excellent mechanical properties under high temperature and high pressure, TZM alloys are extensively applied in the military industry. It is used as the valve body of torpedo engines, rocket nozzles and gas pipelines, where it can withstand extreme thermal and mechanical stresses. It is also used as radiation shields in nuclear applications.
Other molybdenum-based alloys that do not contain iron have only limited applications. For example, because of its resistance to molten zinc, both pure molybdenum and molybdenum-tungsten alloys (70%/30%) are used for piping, stirrers and pump impellers that come into contact with molten zinc.
At least 50 molybdenum-containing enzymes have been identified, mostly in bacteria. Those enzymes include aldehyde oxidase, sulfite oxidase and xanthine oxidase. With one exception, Mo in proteins is bound by molybdopterin to give the molybdenum cofactor. The only known exception is nitrogenase, which uses the FeMoco cofactor, which has the formula Fe7MoS9C.
In terms of function, molybdoenzymes catalyze the oxidation and sometimes reduction of certain small molecules in the process of regulating Nitrogen cycle, Sulfur cycle, and carbon cycle. In some animals, and in humans, the oxidation of xanthine to uric acid, a process of purine catabolism, is catalyzed by xanthine oxidase, a molybdenum-containing enzyme. The activity of xanthine oxidase is directly proportional to the amount of molybdenum in the body. An extremely high concentration of molybdenum reverses the trend and can inhibit purine catabolism and other processes. Molybdenum concentration also affects protein synthesis, metabolism, and growth.
Mo is a component in most . Among molybdoenzymes, nitrogenases are unique in lacking the molybdopterin. (2025). 9789400755604, Springer. ISBN 9789400755604 electronic-book electronic-
(2025). 9789401792684, Springer. ISBN 9789401792684
Nitrogenases catalyze the production of ammonia from atmospheric nitrogen:
Molybdate is transported in the body as MoO42−.
Acute toxicity has not been seen in humans, and the toxicity depends strongly on the chemical state. Studies on rats show a median lethal dose (LD50) as low as 180 mg/kg for some Mo compounds. Although human toxicity data is unavailable, animal studies have shown that chronic ingestion of more than 10 mg/day of molybdenum can cause diarrhea, growth retardation, infertility, low birth weight, and gout; it can also affect the lungs, kidneys, and liver. Sodium tungstate is a competitive inhibitor of molybdenum. Dietary tungsten reduces the concentration of molybdenum in tissues.
Low soil concentration of molybdenum in a geographical band from northern China to Iran results in a general dietary molybdenum deficiency and is associated with increased rates of esophageal cancer. Compared to the United States, which has a greater supply of molybdenum in the soil, people living in those areas have about 16 times greater risk for esophageal squamous cell carcinoma.
Molybdenum deficiency has also been reported as a consequence of non-molybdenum supplemented total parenteral nutrition (complete intravenous feeding) for long periods of time. It results in high blood levels of sulfite and urate, in much the same way as molybdenum cofactor deficiency. Since pure molybdenum deficiency from this cause occurs primarily in adults, the neurological consequences are not as marked as in cases of congenital cofactor deficiency.
A congenital molybdenum cofactor deficiency disease, seen in infants, is an inability to synthesize molybdopterin, the heterocyclic molecule discussed above that binds molybdenum at the active site in all known human enzymes that use molybdenum. The resulting deficiency results in high levels of sulfite and urate, and neurological damage.
Copper reduction or deficiency can also be deliberately induced for therapeutic purposes by the compound ammonium tetrathiomolybdate, in which the bright red anion tetrathiomolybdate is the copper-chelating agent. Tetrathiomolybdate was first used therapeutically in the treatment of copper toxicosis in animals. It was then introduced as a treatment in Wilson's disease, a hereditary copper metabolism disorder in humans; it acts both by competing with copper absorption in the bowel and by increasing excretion. It has also been found to have an inhibitory effect on angiogenesis, potentially by inhibiting the membrane translocation process that is dependent on copper ions. This is a promising avenue for investigation of treatments for cancer, age-related macular degeneration, and other diseases that involve a pathologic proliferation of blood vessels.
In some grazing livestock, most strongly in cattle, molybdenum excess in the soil of pasturage can produce scours (diarrhea) if the pH of the soil is neutral to alkaline; see .
An AI of 2 (μg) of molybdenum per day was established for infants up to 6 months of age, and 3 μg/day from 7 to 12 months of age, both for males and females. For older children and adults, the following daily RDAs have been established for molybdenum: 17 μg from 1 to 3 years of age, 22 μg from 4 to 8 years, 34 μg from 9 to 13 years, 43 μg from 14 to 18 years, and 45 μg for persons 19 years old and older. All these RDAs are valid for both sexes. Pregnancy or Breastfeeding females from 14 to 50 years of age have a higher daily RDA of 50 μg of molybdenum.
As for safety, the NAM sets tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. In the case of molybdenum, the UL is 2000 μg/day. Collectively the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs). (2025). 9780309072793, The National Academies Press. ISBN 9780309072793
The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. AI and UL are defined the same as in the United States. For women and men ages 15 and older, the AI is set at 65 μg/day. Pregnant and lactating women have the same AI. For children aged 1–14 years, the AIs increase with age from 15 to 45 μg/day. The adult AIs are higher than the U.S. RDAs, but on the other hand, the European Food Safety Authority reviewed the same safety question and set its UL at 600 μg/day, which is much lower than the U.S. value.
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