What are the physical properties of molybdenum

what are the physical properties of molybdenum

Chemical Properties

Jul 03,  · Molybdenum Physical Data Density (g/cc). Melting Point (K): Appearance. Covalent Radius (pm). Specific Heat (@20°C J/g mol). Fusion Heat (kJ/mol). Evaporation Heat (kJ/mol). Debye Temperature (K). Pauling Negativity Number. First Ionizing Energy (kJ/mol). Oxidation. Solid molybdenum, which is shaped from the raw powder, has a silvery-white appearance and is extremely hard to the touch, yet is more ductile than other refractory metals such as tungsten. The material has an incredibly high elastic modulus, making it a popular choice for many manufacturing applications. Molybdenum and its alloy family have a number of unique physical properties, such as high strength and resistance to expansion during conditions of elevated temperatures.

Molybdenum is an important alloying agent which 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 moylbdenum and corrosion-resistant nickel-based alloys.

Ferro-molybdenum is used to add hardness and toughness to gun barrels, mo,ybdenum plates, tools, and armor plate. Almost all ultra-high strength steels contain 0. Molybdenum is used in nuclear energy applications and for missile and aircraft parts. Molybdenum oxidizes at elevated temperatures.

Some molybdenum compounds are molybdenim to color pottery and fabrics. Molybdenum is used to make filament supports in incandescent lamps and as filaments in other electrical devices. The metal has found applications as electrodes for electrically-heated glass furnaces. Molybdenum is valuable as a catalyst in there fining of petroleum. The metal is an essential trace element in plant nutrition. Molybdenum sulfide is used as a lubricant, particularly at high temperatures where oils would molybddnum.

Molybdenum forms salts with valencies of 3, 4, or 6, but the hexavalent salts are the most stable. Heat-Resistant Properties Molybdenum is an important alloying agent which contributes to the hardenability and toughness of quenched and tempered steels. This field is for validation purposes and should be left unchanged.

Molybdenum Property & Value:

KEY FACTS. Discovered in by Carl Wilhelm Scheele. First used as armor plating on British tanks in World War I. Has one of the lowest coefficients of thermal expansion of most commercial metals. Molybdenum has a very high melting point so it is produced and sold as a grey powder. Many molybdenum items are formed by compressing the powder at a very high pressure. Physical properties As a solid, molybdenum has a silvery-white metallic appearance. It more commonly occurs as a dark gray or black powder with a metallic luster. Its melting point is about 2,°C (about 4,°F) and the boiling point is 4, to 5,°C (8, to 10,°F).

Molybdenum is a chemical element with the symbol Mo and atomic number The metal was first isolated in by Peter Jacob Hjelm. Molybdenum does not occur naturally as a free metal on Earth; it is found only in various oxidation states in minerals. The free element, a silvery metal with a gray cast, has the sixth-highest melting point of any element. Molybdenum-bearing enzymes 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. In its pure form, molybdenum is a silvery-grey metal with a Mohs hardness of 5. Molybdenum is a transition metal with an electronegativity of 2. It does not visibly react with oxygen or water at room temperature. There are 35 known isotopes of molybdenum, ranging in atomic mass from 83 to , as well as four metastable nuclear isomers.

Seven isotopes occur naturally, with atomic masses of 92, 94, 95, 96, 97, 98, and Of these naturally occurring isotopes, only molybdenum is unstable. Molybdenum is the most abundant isotope, comprising Molybdenum has a half-life of about 10 19 y and undergoes double beta decay into ruthenium All unstable isotopes of molybdenum decay into isotopes of niobium , technetium , and ruthenium. Of the synthetic radioisotopes , the most stable is 93 Mo, with a half-life of 4, years.

The most common isotopic molybdenum application involves molybdenum , which is a fission product. It is a parent radioisotope to the short-lived gamma-emitting daughter radioisotope technetiumm , a nuclear isomer used in various imaging applications in medicine.

Higher oxidation states are more relevant to its terrestrial occurrence and its biological roles, mid-level oxidation states are often associated with metal clusters , and very low oxidation states are typically associated with organomolybdenum compounds.

Mo and W chemistry shows strong similarities. The highest oxidation state is seen in molybdenum VI oxide MoO 3 , whereas the normal sulfur compound is molybdenum disulfide MoS 2.

From the perspective of commerce, the most important compounds are molybdenum disulfide MoS 2 and molybdenum trioxide MoO 3. The black disulfide is the main mineral. It is roasted in air to give the trioxide: [19]. The trioxide, which is volatile at high temperatures, is the precursor to virtually all other Mo compounds as well as alloys.

Molybdates are weaker oxidants than chromates. Polymolybdates can incorporate other ions, forming polyoxometalates. The oxidation state 0 is possible with carbon monoxide as ligand, such as in molybdenum hexacarbonyl , Mo CO 6.

Molybdenite —the principal ore from which molybdenum is now extracted—was previously known as molybdena. Molybdena was confused with and often utilized as though it were graphite. Like graphite, molybdenite can be used to blacken a surface or as a solid lubricant. Although reportedly molybdenum was deliberately alloyed with steel in one 14th-century Japanese sword mfd.

By Swedish chemist Carl Wilhelm Scheele stated firmly that molybdena was indeed neither galena nor graphite. Peter Jacob Hjelm successfully isolated molybdenum using carbon and linseed oil in 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.

In , William D. Coolidge filed a patent for rendering molybdenum ductile , 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.

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 armor plating and as a substitute for tungsten in high speed steels.

Some British tanks were protected by 75 mm 3 in manganese steel plating, but this proved to be ineffective. The manganese steel plates were replaced with much lighter 25 mm 1. In World War II , molybdenum again saw strategic importance as a substitute for tungsten in steel alloys.

Molybdenum is the 54th most abundant element in the Earth's crust with an average of 1. Molybdenum is mined as a principal ore and is also recovered as a byproduct of copper and tungsten mining.

The world's production of molybdenum was , tonnes in , the largest producers being China 94, t , the United States 64, t , Chile 38, t , Peru 18, t and Mexico 12, t. The total reserves are estimated at 10 million tonnes, and are mostly concentrated in China 4. The process gives gaseous sulfur dioxide and the molybdenum VI oxide : [19]. Copper, an impurity in molybdenite, is less soluble in ammonia. To completely remove it from the solution, it is precipitated with hydrogen sulfide.

Heating this solid gives molybdenum trioxide: [45]. The molybdenum for steel production is reduced by the aluminothermic reaction with addition of iron to produce ferromolybdenum. Historically, the Knaben mine in southern Norway, opened in , was the first dedicated molybdenum mine. It was closed in but was reopened in Large mines in Colorado such as the Henderson mine and the Climax mine [50] and in British Columbia yield molybdenite as their primary product, while many porphyry copper deposits such as the Bingham Canyon Mine in Utah and the Chuquicamata mine in northern Chile produce molybdenum as a byproduct of copper mining.

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 alloys for example, 41xx steels contain 0. Molybdenum is also valued in steel alloys for its high corrosion resistance and weldability.

Molybdenum increases lattice strain, thus increasing the energy required to dissolve iron atoms from the surface. Because of its lower density and more stable price, molybdenum is sometimes used in place of tungsten. Molybdenum can also be used as a flame-resistant coating for other metals. 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 hours with so little corrosion that it was difficult to measure.

Other molybdenum-based alloys that do not contain iron have only limited applications. Molybdenum is an essential element in most organisms; a research paper speculated that a scarcity of molybdenum in the Earth's early oceans may have strongly influenced the evolution of eukaryotic life which includes all plants and animals. At least 50 molybdenum-containing enzymes have been identified, mostly in bacteria.

In terms of function, molybdoenzymes catalyze the oxidation and sometimes reduction of certain small molecules in the process of regulating nitrogen , sulfur , and carbon. The activity of xanthine oxidase is directly proportional to the amount of molybdenum in the body.

However, an extremely high concentration of molybdenum reverses the trend and can act as an inhibitor in both purine catabolism and other processes. Molybdenum concentration also affects protein synthesis , metabolism , and growth. Mo is a component in most nitrogenases. Among molybdoenzymes, nitrogenases are unique in lacking the molybdopterin. The biosynthesis of the FeMoco active site is highly complex. Molybdenum is an essential trace dietary element. Acute toxicity has not been seen in humans, and the toxicity depends strongly on the chemical state.

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. 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. However presumably 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.

Most molybdenum is excreted as molybdate from the body in the urine. Furthermore, urinary excretion of molybdenum increases as dietary molybdenum intake increases. Small amounts of molybdenum are excreted from the body in the feces by way of the bile; small amounts also can be lost in sweat and in hair. A congenital molybdenum cofactor deficiency disease, seen in infants, is an inability to synthesize molybdenum cofactor , 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. High levels of molybdenum can interfere with the body's uptake of copper , producing copper deficiency. Molybdenum prevents plasma proteins from binding to copper, and it also increases the amount of copper that is excreted in urine. Ruminants that consume high levels of molybdenum suffer from diarrhea , stunted growth, anemia , and achromotrichia loss of fur pigment.

These symptoms can be alleviated by copper supplements, either dietary and injection. 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.

In , the then U. All these RDAs are valid for both sexes. As for safety, the NAM sets tolerable upper intake levels ULs for vitamins and minerals when evidence is sufficient.

Pregnant and lactating women have the same AI. The adult AIs are higher than the U. For U. Other significant dietary sources include green beans, eggs, sunflower seeds, wheat flour, lentils, cucumbers, and cereal grain.





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