Molybdenum

  • molybdenum, 42mo
    molybdenum crystaline fragment and 1cm3 cube.jpg
    molybdenum
    pronunciationm/ (lib-dən-əm)
    appearancegray metallic
    standard atomic weight ar, std(mo)95.95(1)[1]
    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 molybdenum 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
    niobiummolybdenumtechnetium
    atomic number (z)42
    groupgroup 6
    periodperiod 5
    blockd-block
    element category  transition metal
    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 (near r.t.)10.28 g/cm3
    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 states−4, −2, −1, 0, +1,[2] +2, +3, +4, +5, +6 (a strongly acidic oxide)
    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
    color lines in a spectral range
    spectral lines of molybdenum
    other properties
    natural occurrenceprimordial
    crystal structurebody-centered cubic (bcc)
    body-centered cubic crystal structure for molybdenum
    speed of sound thin rod5400 m/s (at r.t.)
    thermal expansion4.8 µm/(m·k) (at 25 °c)
    thermal conductivity138 w/(m·k)
    thermal diffusivity54.3 mm2/s (at 300 k)[3]
    electrical resistivity53.4 nΩ·m (at 20 °c)
    magnetic orderingparamagnetic[4]
    magnetic susceptibility+89.0·10−6 cm3/mol (298 k)[5]
    young's modulus329 gpa
    shear modulus126 gpa
    bulk modulus230 gpa
    poisson ratio0.31
    mohs hardness5.5
    vickers hardness1400–2740 mpa
    brinell hardness1370–2500 mpa
    cas number7439-98-7
    history
    discoverycarl wilhelm scheele (1778)
    first isolationpeter jacob hjelm (1781)
    main isotopes of molybdenum
    iso­tope abun­dance half-life (t1/2) decay mode pro­duct
    92mo 14.65% stable
    93mo syn 4×103 y ε 93nb
    94mo 9.19% stable
    95mo 15.87% stable
    96mo 16.67% stable
    97mo 9.58% stable
    98mo 24.29% stable
    99mo syn 65.94 h β 99mtc
    γ
    100mo 9.74% 7.8×1018 y ββ 100ru
    | references

    molybdenum is a chemical element with the symbol mo and atomic number 42. the name is from neo-latin molybdaenum, from ancient greek Μόλυβδος molybdos, meaning lead, since its ores were confused with lead ores.[6] 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.[7]

    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. it readily forms hard, stable carbides in alloys, and for this reason most of 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, but when molybdenum-bearing minerals contact oxygen and water, the resulting molybdate ion moo2−
    4
    is quite soluble. industrially, molybdenum compounds (about 14% of world production of the element) are used in high-pressure and high-temperature applications 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. these nitrogenases contain molybdenum in a form different from other molybdenum enzymes, which all contain fully oxidized molybdenum in a molybdenum cofactor. these various molybdenum cofactor enzymes are vital to the organisms, and molybdenum is an essential element for life in all higher eukaryote organisms, though not in all bacteria.

  • characteristics
  • compounds
  • history
  • occurrence and production
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Molybdenum, 42Mo
Molybdenum crystaline fragment and 1cm3 cube.jpg
Molybdenum
Pronunciationm/ (LIB-dən-əm)
Appearancegray metallic
Standard atomic weight Ar, std(Mo)95.95(1)[1]
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 Molybdenum 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
niobiummolybdenumtechnetium
Atomic number (Z)42
Groupgroup 6
Periodperiod 5
Blockd-block
Element category  Transition metal
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 (near r.t.)10.28 g/cm3
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 states−4, −2, −1, 0, +1,[2] +2, +3, +4, +5, +6 (a strongly acidic oxide)
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
Color lines in a spectral range
Spectral lines of molybdenum
Other properties
Natural occurrenceprimordial
Crystal structurebody-centered cubic (bcc)
Body-centered cubic crystal structure for molybdenum
Speed of sound thin rod5400 m/s (at r.t.)
Thermal expansion4.8 µm/(m·K) (at 25 °C)
Thermal conductivity138 W/(m·K)
Thermal diffusivity54.3 mm2/s (at 300 K)[3]
Electrical resistivity53.4 nΩ·m (at 20 °C)
Magnetic orderingparamagnetic[4]
Magnetic susceptibility+89.0·10−6 cm3/mol (298 K)[5]
Young's modulus329 GPa
Shear modulus126 GPa
Bulk modulus230 GPa
Poisson ratio0.31
Mohs hardness5.5
Vickers hardness1400–2740 MPa
Brinell hardness1370–2500 MPa
CAS Number7439-98-7
History
DiscoveryCarl Wilhelm Scheele (1778)
First isolationPeter Jacob Hjelm (1781)
Main isotopes of molybdenum
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
92Mo 14.65% stable
93Mo syn 4×103 y ε 93Nb
94Mo 9.19% stable
95Mo 15.87% stable
96Mo 16.67% stable
97Mo 9.58% stable
98Mo 24.29% stable
99Mo syn 65.94 h β 99mTc
γ
100Mo 9.74% 7.8×1018 y ββ 100Ru
| references

Molybdenum is a chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin molybdaenum, from Ancient Greek Μόλυβδος molybdos, meaning lead, since its ores were confused with lead ores.[6] 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.[7]

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. It readily forms hard, stable carbides in alloys, and for this reason most of 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, but when molybdenum-bearing minerals contact oxygen and water, the resulting molybdate ion MoO2−
4
is quite soluble. Industrially, molybdenum compounds (about 14% of world production of the element) are used in high-pressure and high-temperature applications 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. These nitrogenases contain molybdenum in a form different from other molybdenum enzymes, which all contain fully oxidized molybdenum in a molybdenum cofactor. These various molybdenum cofactor enzymes are vital to the organisms, and molybdenum is an essential element for life in all higher eukaryote organisms, though not in all bacteria.