Molybdenum

Molybdenum, 42Mo
Molybdenum
Pronunciation/məˈlɪbdənəm/ ⓘ ​(mə-LIB-də-nəm)
Appearancegray metallic
Standard atomic weight Ar°(Mo)
  • 95.95±0.01[1]
  • 95.95±0.01 (abridged)[2]
Molybdenum in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Cr
↑
Mo
↓
W
niobium ← molybdenum → technetium
Atomic number (Z)42
Groupgroup 6
Periodperiod 5
Block  d-block
Electron configuration[Kr] 4d5 5s1
Electrons per shell2, 8, 18, 13, 1
Physical properties
Phase at STPsolid
Melting point2896 K ​(2623 °C, ​4753 °F)
Boiling point4912 K ​(4639 °C, ​8382 °F)
Density (at 20° C)10.223 g/cm3[3]
when liquid (at m.p.)9.33 g/cm3
Heat of fusion37.48 kJ/mol
Heat of vaporization598 kJ/mol
Molar heat capacity24.06 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 2742 2994 3312 3707 4212 4879
Atomic properties
Oxidation statescommon: +4, +6
−4,[4] −2,[5] −1,[5] 0,[6] +1,[5] +2,[5] +3,[5] +5[5]
ElectronegativityPauling scale: 2.16
Ionization energies
  • 1st: 684.3 kJ/mol
  • 2nd: 1560 kJ/mol
  • 3rd: 2618 kJ/mol
Atomic radiusempirical: 139 pm
Covalent radius154±5 pm
Spectral lines of molybdenum
Other properties
Natural occurrenceprimordial
Crystal structure ​body-centered cubic (bcc) (cI2)
Lattice constant
a = 314.71 pm (at 20 °C)[3]
Thermal expansion5.10×10−6/K (at 20 °C)[3]
Thermal conductivity138 W/(m⋅K)
Thermal diffusivity54.3 mm2/s (at 300 K)[7]
Electrical resistivity53.4 nΩ⋅m (at 20 °C)
Magnetic orderingparamagnetic[8]
Molar magnetic susceptibility+89.0×10−6 cm3/mol (298 K)[9]
Young's modulus329 GPa
Shear modulus126 GPa
Bulk modulus230 GPa
Speed of sound thin rod5400 m/s (at r.t.)
Poisson ratio0.31
Mohs hardness5.5
Vickers hardness1400–2740 MPa
Brinell hardness1370–2500 MPa
CAS Number7439-98-7
History
Namingfrom Greek Μόλυβδος, 'lead', since its ores were confused with lead ores
DiscoveryCarl Wilhelm Scheele (1778)
First isolationPeter Jacob Hjelm (1781)
Isotopes of molybdenum
Main isotopes[10] Decay
Isotope abun­dance half-life (t1/2) mode pro­duct
92Mo 14.7% stable
93Mo synth 4839 y[11] ε 93Nb
94Mo 9.19% stable
95Mo 15.9% stable
96Mo 16.7% stable
97Mo 9.58% stable
98Mo 24.3% stable
99Mo synth 65.932 h β− 99mTc
100Mo 9.74% 7.07×1018 y β−β− 100Ru

Molybdenum is a chemical element; it has symbol Mo (from Neo-Latin molybdaenum) and atomic number 42. The name derived from Ancient Greek μόλυβδος mólybdos, meaning lead, since its ores were sometimes confused with those of lead.[12] 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.[13]

Molybdenum does not occur naturally as a free metal on Earth; in its minerals, it is found only in oxidized states. The free element, a silvery metal with a grey cast, has the sixth-highest melting point of any element. It readily forms hard, stable carbides in alloys, and for this reason most of the world production of the element (about 80%) is used in steel alloys, including high-strength alloys and superalloys.

Most molybdenum compounds have low solubility in water. Heating molybdenum-bearing minerals under oxygen and water affords molybdate ion MoO2−
4, which forms quite soluble salts. Industrially, molybdenum compounds (about 14% of world production of the element) are used as pigments and catalysts.

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. Most nitrogenases contain an iron–molybdenum cofactor FeMoco, which is believed to contain either Mo(III) or Mo(IV).[14][15] By contrast Mo(VI) and Mo(IV) are complexed with molybdopterin in all other molybdenum-bearing enzymes.[16] Molybdenum is an essential element for all higher eukaryote organisms, including humans. A species of sponge, Theonella conica, is known for hyperaccumulation of molybdenum.[17]

  1. ^ "Standard Atomic Weights: Molybdenum". CIAAW. 2013.
  2. ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  3. ^ a b c Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
  4. ^ Mo(–4) occurs in Na4Mo(CO)4; see John E. Ellis (2003). "Metal Carbonyl Anions: from [Fe(CO)4]2− to [Hf(CO)6]2− and Beyond†". Organometallics. 22 (17): 3322–3338. doi:10.1021/om030105l.
  5. ^ a b c d e f Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. doi:10.1016/C2009-0-30414-6. ISBN 978-0-08-037941-8.
  6. ^ Mo(0) occurs in molybdenum hexacarbonyl; see John E. Ellis (2003). "Metal Carbonyl Anions: from [Fe(CO)4]2− to [Hf(CO)6]2− and Beyond†". Organometallics. 22 (17): 3322–3338. doi:10.1021/om030105l.
  7. ^ Lindemann, A.; Blumm, J. (2009). Measurement of the Thermophysical Properties of Pure Molybdenum. Vol. 3. 17th Plansee Seminar.
  8. ^ Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
  9. ^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  10. ^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3) 030001. doi:10.1088/1674-1137/abddae.
  11. ^ Kajan, I.; Heinitz, S.; Kossert, K.; Sprung, P.; Dressler, R.; Schumann, D. (2021-10-05). "First direct determination of the 93Mo half-life". Scientific Reports. 11 (1). doi:10.1038/s41598-021-99253-5. ISSN 2045-2322. PMC 8492754. PMID 34611245.
  12. ^ Lide, David R., ed. (1994). "Molybdenum". CRC Handbook of Chemistry and Physics. Vol. 4. Chemical Rubber Publishing Company. p. 18. ISBN 978-0-8493-0474-3.
  13. ^ "It's Elemental – The Element Molybdenum". Science Education at Jefferson Lab. Archived from the original on 2018-07-04. Retrieved 2018-07-03.
  14. ^ Bjornsson, Ragnar; Neese, Frank; Schrock, Richard R.; Einsle, Oliver; DeBeer, Serena (2015). "The discovery of Mo(III) in FeMoco: reuniting enzyme and model chemistry". Journal of Biological Inorganic Chemistry. 20 (2): 447–460. doi:10.1007/s00775-014-1230-6. ISSN 0949-8257. PMC 4334110. PMID 25549604.
  15. ^ Van Stappen, Casey; Davydov, Roman; Yang, Zhi-Yong; Fan, Ruixi; Guo, Yisong; Bill, Eckhard; Seefeldt, Lance C.; Hoffman, Brian M.; DeBeer, Serena (2019-09-16). "Spectroscopic Description of the E1 State of Mo Nitrogenase Based on Mo and Fe X-ray Absorption and Mössbauer Studies". Inorganic Chemistry. 58 (18): 12365–12376. doi:10.1021/acs.inorgchem.9b01951. ISSN 0020-1669. PMC 6751781. PMID 31441651.
  16. ^ Leimkühler, Silke (2020). "The biosynthesis of the molybdenum cofactors in Escherichia coli". Environmental Microbiology. 22 (6): 2007–2026. Bibcode:2020EnvMi..22.2007L. doi:10.1111/1462-2920.15003. ISSN 1462-2920. PMID 32239579.
  17. ^ Shoham, Shani; Keren, Ray; Lavy, Adi; Polishchuk, Iryna; Pokroy, Boaz; Ilan, Micha (2024-07-19). "Out of the blue: Hyperaccumulation of molybdenum in the Indo-Pacific sponge Theonella conica". Science Advances. 10 (29) eadn3923. Bibcode:2024SciA...10N3923S. doi:10.1126/sciadv.adn3923. ISSN 2375-2548. PMC 466961. PMID 39018411.
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