Molybdenum, Molybdenum Information, Molybdenum Wiki

News, World News by www.WorldOfNews.com

Rainbow-powered solar cells come closer to reality - aniin.com

Brakes India to expand Oman foundry facility - IANS.in

Think tank to drum up new uses for molybdenum - Reuters

Metal firm increases profit on demand - ShanghaiDaily

Shares of Thompson Creek Metals fall as second-quarter earnings miss estimates - SingaporeStar

Piping hot - ShanghaiDaily

Molybdenum prices may rise on strong demand - BusinessLine

More >>


Latino Music - Shopping, LATINO - Latino Chat If you are looking for latino chat, you will enter the �latino musica� world. You can find here any latino music song you want., here is the right place to be. If you enter our site
Advertising Photographer - Shopping, Wedding Photographer
METAL - Metal Building, Metal Detector - Shopping, Full Metal Alchemist

niobium ← molybdenum → technetium

Cr
↑
Mo
↓
W

Periodic Table - Extended Periodic Table

General

Name, Symbol, Number

molybdenum, Mo, 42

Chemical series

transition metals

Group, Period, Block

6, 5, d

Appearance

gray metallic

Standard atomic weight

95.94 (2) g·mol⁻¹

Electron configuration

[Kr] 4d⁵ 5s¹

Electrons per shell

2, 8, 18, 13, 1

Physical properties

Phase

solid

Density (near r.t.)

10.28 g·cm⁻³

Liquid density at m.p.

9.33 g·cm⁻³

Melting point

2896 K
(2623 °C, 4753 °F)

Boiling point

4912 K
(4639 °C, 8382 °F)

Heat of fusion

37.48 kJ·mol⁻¹

Heat of vaporization

617 kJ·mol⁻¹

Heat capacity

(25 °C) 24.06 J·mol⁻¹·K⁻¹

Vapor pressure
P(Pa)	1	10	100	1 k	10 k	100 k
at T(K)	2742	2994	3312	3707	4212	4879

Atomic properties

Crystal structure

cubic body centered

Oxidation states

6, 5, 4, 3, 2, 1Molybdenum: molybdenum(I) fluoride compound data. OpenMOPAC.net. Retrieved on 2007-12-10.
(strongly acidic oxide)

Electronegativity

2.16 (Pauling scale)

Ionization energies
(more)

1st: 684.3 kJ·mol⁻¹

2nd: 1560 kJ·mol⁻¹

3rd: 2618 kJ·mol⁻¹

Atomic radius

145 pm

Atomic radius (calc.)

190 pm

Covalent radius

145 pm

Miscellaneous

Magnetic ordering

no data

Electrical resistivity

(20 °C) 53.4 n Ω·m

Thermal conductivity

(300 K) 138 W·m⁻¹·K⁻¹

Thermal expansion

(25 °C) 4.8 µm·m⁻¹·K⁻¹

Speed of sound (thin rod)

(r.t.) 5400 m·s⁻¹

329 GPa

126 GPa

230 GPa

0.31

5.5

1530 MPa

1500 MPa

7439-98-7

Selected isotopes

Main article: Isotopes of molybdenum
iso	NA	half-life	DM	DE (MeV)	DP
⁹²Mo	14.84%	⁹²Mo is stable with 50 neutrons
⁹³Mo	syn	4×10³ y	ε	-	⁹³Nb
⁹⁴Mo	9.25%	⁹⁴Mo is stable with 52 neutrons
⁹⁵Mo	15.92%	⁹⁵Mo is stable with 53 neutrons
⁹⁶Mo	16.68%	⁹⁶Mo is stable with 54 neutrons
⁹⁷Mo	9.55%	⁹⁷Mo is stable with 55 neutrons
⁹⁸Mo	24.13%	⁹⁸Mo is stable with 56 neutrons
⁹⁹Mo	syn	65.94 h	β^-	0.436, 1.214	⁹⁹Tc
⁹⁹Mo	syn	65.94 h	γ	0.74, 0.36, 0.14	-
¹⁰⁰Mo	9.63%	7.8×10¹⁸ y	β^-β^-	3.04	¹⁰⁰Ru

References

Molybdenum (pronounced /məˈlɪbdənəm/, from the Greek meaning "lead-like"), is a Group 6 chemical element with the symbol Mo and atomic number 42. It has the sixth-highest melting point of any element, and for this reason it is often used in high-strength steel alloys. Molybdenum is found in trace amounts in plants and animals, although excess molybdenum can be toxic in some animals. Molybdenum was discovered in 1778 by Carl Wilhelm Scheele and first isolated in 1781 by Peter Jacob Hjelm.

Characteristics

Molybdenum is a transition metal with an electronegativity of 1.8 on the Pauling scale and an atomic mass of 95.9 g/mole.Properties of Molybdenum. Integral Scientist Periodic Table. Qivx, Inc. (2003). Retrieved on 2007-06-10. It does not react with oxygen or water at room temperature. At elevated temperatures, molybdenum trioxide is formed in the reaction 2Mo + 3O₂ → 2MoO₃.Winter, Mark. Chemistry. Molybdenum. The University of Sheffield. Retrieved on 2007-06-10.

In its pure metal form, molybdenum is silvery white and very hard, though it is somewhat more ductile than tungsten. It has a melting point of 2623°C, and only tantalum, osmium, rhenium, and tungsten have higher melting points. Molybdenum burns only at temperatures above 600°C.Considine, Glenn D., ed. (2005), "Molybdenum", Van Nostrand\'s Encyclopedia of Chemistry, New York: Wylie-Interscience, pp. 1038-1040, 0-471-61525-0 It also has the lowest heating expansion of any commercially used metal.

Molybdenum has a value of approximately $65,000 per tonne as of 4 May 2007. It maintained a price at or near $10,000 per tonne from 1997 through 2002, and reached a high of $103,000 per tonne in June 2005.Dynamic Prices and Charts for Molybdenum. InfoMine Inc. (2007). Retrieved on 2007-05-07.

Isotopes

Main article: Isotopes of molybdenum

There are 35 known isotopes of molybdenum ranging in atomic mass from 83 to 117, as well as four metastable nuclear isomers. Seven isotopes occur naturally, with atomic masses of 92, 94, 95, 96, 97, 98, and 100. Of these naturally occurring isotopes, five are stable, with atomic masses from 94 to 98. All unstable isotopes of molybdenum decay into isotopes of niobium, technetium, and ruthenium.Lide, David R., ed. (2006), CRC Handbook of Chemistry and Physics, vol. 11, CRC, pp. 87-88, 0-8493-0487-3

Molybdenum-92 and molybdenum-100 are the only naturally occurring isotopes that are not stable. Molybdenum-100 has a half-life of approximately 1×10¹⁹ y and undergoes double beta decay into ruthenium-100. Molybdenum-98 is the most common isotope, comprising 24.14% of all molybdenum. Molybdenum isotopes with mass numbers from 111 to 117 all have half-lives of approximately .15 μs.

Occurrence

Molybdenum output in 2005

The world\'s largest producers of molybdenum materials are the United States, Canada, Chile, Russia, and China.Lide, David R., ed. (2006), CRC Handbook of Chemistry and Physics, vol. 4, Chemical Rubber Publishing Company, pp. 22-23, 0-8493-0487-3Emsley, John (2001). Nature\'s Building Blocks. Oxford: Oxford University Press, 262-266. 0-19-850341-5.

Though molybdenum is found in such minerals as wulfenite (PbMoO₄) and powellite (CaMoO₄), the main commercial source of molybdenum is molybdenite (MoS₂). Molybdenum is mined as a principal ore, and is also recovered as a byproduct of copper and tungsten mining. The large mining areas in Colorado (Climax) and in British Columbia yield molybdenite while the Chuquicamata mines in northern Chile produce molybdenum as a byproduct of copper mining. The Knaben mine in southern Norway was opened in 1885, making it the first molybdenum mine. It remained open until 1973.

Molybdenum is the 42nd-most-abundant element in the universe, and the 25th-most-abundant element in Earth\'s oceans, with an average of 10.8 mt/km³. The Russian Luna 24 mission discovered a single molybdenum-bearing grain (1 × 0.6 µm) in a pyroxene fragment taken from Mare Crisium on the Moon.American Mineralogist, Volume 87, pages 181-184, 2002. Retrieved on 2007-04-09.

A side product of molybdenum mining is rhenium. As it is always present in small varying quantities in molybdenite, the only commercial source for rhenium is molybdenum mines.

Compounds

See also: Category:Molybdenum compounds

Please help improve this article or section by expanding it.
Further information might be found on the talk page or at requests for expansion. (December 2007)

Molybdenum has several common oxidation states, +2 +3 +4 +5 and +6. The highest oxidation state is common in the molybdenum(VI) oxide MoO₃ while the normal sulfur compound is molybdenum disulfide MoS₂. The broad range of oxidation states shows up in the chlorides of molybdenum:

Molybdenum(II) chloride MoCl₂ (yellow solid),
Molybdenum(III) chloride MoCl₃ (dark red solid),
Molybdenum(V) chloride MoCl₅ (dark green solid),
Molybdenum(IV) chloride MoCl₆ (brown solid),

Like chromium and some other transition metals molybdenum is able to form quadruple bonds

Biological role

The most important use of the molybdenum atom in in living organisms is as a metal hetero-atom at the active site in certain in enzymes. In nitrogen fixation in certain bacteria, the nitrogenase enzyme which is involved in the terminal step of reducing molecular nitrogen, usually contains molybdenum in the active site (though replacement of Mo with iron or vanadium is known).

Though molybdenum forms compounds with various organic molecules, including carbohydrates and amino acids, it is transported throughout the human body as MoO₄^2-.Mitchell, Phillip C. H. (2003). Overview of Environment Database. International Molybdenum Association. Retrieved on 2007-05-05. Molybdenum is present in approximately 20 enzymes in animals, including aldehyde oxidase, sulfite oxidase, xanthine oxidase. In some animals, 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. However, an extremely high concentration of molybdenum reverses the trend, and can act as an inhibitor in both purine catabolism and other processes. Molybdenum concentrations also affect protein synthesis, metabolism, and growth.

In a 70 kg human body, there is approximately 9.3 mg molybdenum, comprising .00001% of the total body mass.Lide, David R., ed. (2006), CRC Handbook of Chemistry and Physics, vol. 7, Chemical Rubber Publishing Company, pp. 18, 0-8493-0487-3 It occurs in higher concentrations in the liver and kidneys, and in lower concentrations in the vertebrae. Molybdenum is also present within human tooth enamel and may help prevent the decaying thereof.Ismail, Mumtaz. Dental Problems and Diet. Health and Nutrition. Bawarchi. Retrieved on 2007-05-19. Pork, lamb, and beef liver each have approximately 1.5 parts molybdenum per million. Other significant dietary sources include green beans, eggs, sunflower seeds, wheat flour, lentils, and cereal grain.

The average daily intake of molybdenum is .3 mg. Daily intake above .4 mg can be toxic. Molybdenum deficiency, caused by less than .05 mg/day, can cause stunted growth, reduced appetite, and impaired reproduction.Guide to Healthy Minerals. Cherokee Naturals. Retrieved on 2007-05-17. Sodium tungstate is a competitive inhibitor of molybdenum. Dietary tungsten reduces the concentration of molybdenum in tissues.

Copper-molybdenum antagonism

High amounts of molybdenum can interfere with the body\'s uptake of copper, both by preventing plasma proteins from binding the copper and by increasing the amount of copper that is excreted in urine. Ruminants that consume high amounts of molybdenum develop symptoms including diarrhea, stunted growth, anemia, and achromotrichia. These symptoms can be alleviated by the administration of more copper into the system, both in dietary form and by injection.Suttle, N. F. (December 1974). "Recent studies of the copper-molybdenum antagonism". Proceedings of the Nutrition Society 33 (3): 299-305. CABI Publishing. doi:10.1079/PNS19740053. Retrieved on 2007-05-11. The condition can be aggravated by excess sulfur.

Applications

The ability of molybdenum to withstand extreme temperatures without significantly expanding or softening makes it useful in applications that involve intense heat, including the manufacture of aircraft parts, electrical contacts, industrial motors, and filaments. Molybdenum is also used in alloys for its high corrosion resistance and weldability.Molybdenum Statistics and Information. U.S. Geological Survey (2007-05-10). Retrieved on 2007-05-10. Most high-strength steel alloys are .25% to 8% molybdenum. Despite being used in such small portions, more than 43 million kg of molybdenum is used as an alloying agent each year in stainless steels, tool steels, cast irons, and high-temperature superalloys.

Because of its lower density and more stable price, molybdenum is implemented in the place of tungsten. Molybdenum can be implemented both as an alloying agent and as a flame-resistant coating for other metals. Although its melting point is 2623 °C, molybdenum rapidly oxidizes at temperatures above 760 °C, making it better-suited for use in vacuum environments.Molybdenum. AZoM.com Pty. Limited (2007). Retrieved on 2007-05-06.

Molybdenum disulfide (MoS₂) is used as a lubricant and an agent. It forms strong films on metallic surfaces, and is highly resistant to both extreme temperatures and high pressure. Lead molybdate co-precipitated with lead chromate and lead sulfate is a bright-orange pigment used with ceramics and plastics. International Molybdenum Association, www.moly.imoa.info Molybdenum trioxide (MoO₃) is used as an adhesive between enamels and metals. Molybdenum powder is used as a fertilizer for some plants, such as cauliflower.

Also used in NO, NO2, NOx analyzers in power plants for pollution controls. At 350 °C the element acts as a catalyst for NO2/NOx to form only NO molecules for consistent readings by infrared light.

History

Molybdenite (from the Greek Μόλυβδος molybdos, meaning lead),Lide, David R., ed. (1994), "Molybdenum", CRC Handbook of Chemistry and Physics, vol. 4, Chemical Rubber Publishing Company, pp. 18, 0-8493-0474-1 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.Van der Krogt, Peter (2006-01-10). Molybdenum. Elementymology & Elements Multidict. Retrieved on 2007-05-20.

It was not until 1778 that Swedish chemist Carl Wilhelm Scheele realized molybdena was neither graphite nor lead.Gagnon, Steve. Molybdenum. Jefferson Science Associates, LLC. Retrieved on 2007-05-06.C. W. K. Scheele (1779). "Versuche mit Wasserbley;Molybdaena". svenska vetensk. Academ. Handlingar 40: 238. 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.P. J. Hjelm (1788). "Versuche mit Molybdäna, und Reduction der selben Erde". svenska vetensk. Academ. Handlingar 49: 268. For a long time there was no industrial use for molybdenum. The French Schneider Electrics company produced the first steel molybdenum alloy armor plates in 1894. Until World War I most other armor factories also used molybdenum alloys. 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 maneuverability, and, despite being thinner, better protection. The high demand of molybdenum in World War I and World War II and the steep decrease after the wars had a great influence on prices and production of molybdenum.

Precautions

Molybdenum dusts and fumes, as can be generated by mining or metalworking, are not toxic. There are no long-term effects associated with exposure to molybdenum; however, prolonged exposure can cause irritation to the eyes and skin. The direct inhalation or ingestion of molybdenum should also be avoided.Material Safety Data Sheet - Molybdenum. The REMBAR Company, Inc. (2000-09-19). Retrieved on 2007-05-13. OSHA regulations specify the maximum permissible molybdenum exposure in an 8-hour day to be 5 mg/m³. Chronic exposure to 60 to 600 mg Mo/m³ can cause symptoms including fatigue, headaches, and joint pains.NIOSH Documentation for ILDHs Molybdenum. National Institute for Occupational Safety and Health (1996-08-16). Retrieved on 2007-05-31.