Molybdenum

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Molybdenum
42Mo
Cr

Mo

W
niobiummolybdenumtechnetium
Appearance
gray metallic
General properties
Name, seembol, nummer molybdenum, Mo, 42
Pronunciation /ˌmɒlɪbˈdnəm/ MOL-ib-DEE-nəm
or /məˈlɪbdɨnəm/ mə-LIB-di-nəm
Element category transeetion metal
Group, period, block 6, 5, d
Staundart atomic wicht 95.95(1)
Electron confeeguration [Kr] 5s1 4d5
2, 8, 18, 13, 1
Electron shells of molybdenum (2, 8, 18, 13, 1)
History
Discovery Carl Wilhelm Scheele (1778)
First isolation Peter Jacob Hjelm (1781)
Physical properties
Phase solid
Density (near r.t.) 10.28 g·cm−3
Liquid density at m.p. 9.33 g·cm−3
Meltin pynt 2896 K, 2623 °C, 4753 °F
Boilin pynt 4912 K, 4639 °C, 8382 °F
Heat o fusion 37.48 kJ·mol−1
Heat o vaporization 598 kJ·mol−1
Molar heat capacity 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
Oxidation states 6, 5, 4, 3, 2, 1[1], -1, -2
(strongly acidic oxide)
Electronegativity 2.16 (Pauling scale)
Ionization energies 1st: 684.3 kJ·mol−1
2nd: 1560 kJ·mol−1
3rd: 2618 kJ·mol−1
Atomic radius 139 pm
Covalent radius 154±5 pm
Miscellanea
Crystal structure body-centered cubic
Molybdenum has a body-centered cubic crystal structure
Magnetic orderin paramagnetic[2]
Electrical resistivity (20 °C) 53.4 nΩ·m
Thermal conductivity 138 W·m−1·K−1
Thermal diffusivity (300 K) 54.3[3] mm²/s
Thermal expansion (25 °C) 4.8 µm·m−1·K−1
Speed o soond (thin rod) (r.t.) 5400 m·s−1
Young's modulus 329 GPa
Shear modulus 126 GPa
Bulk modulus 230 GPa
Poisson ratio 0.31
Mohs hairdness 5.5
Vickers hairdness 1530 MPa
Brinell hairdness 1500 MPa
CAS registry nummer 7439-98-7
Most stable isotopes
Main article: Isotopes o molybdenum
iso NA hauf-life DM DE (MeV) DP
92Mo 14.84% >1.9×1020 y (β+β+) 1.6491 92Zr
93Mo syn 4×103 y ε - 93Nb
94Mo 9.25% - (SF) <4.485
95Mo 15.92% - (SF) <4.531
96Mo 16.68% - (SF) <5.771
97Mo 9.55% - (SF) <6.226
98Mo 24.13% >1×1014 y ββ 0.1125 98Ru
99Mo syn 65.94 h β 0.436, 1.214 99mTc
γ 0.74, 0.36,
0.14
-
100Mo 9.63% 7.8×1018 y (ββ) 3.04 100Ru
Decay modes in parentheses are predicted, but have not yet been observed
· r

Molybdenum is a Group 6 chemical element wi the seembol Mo an atomic nummer 42. The name is frae Neo-Laitin Molybdaenum, frae Auncient Greek Μόλυβδος molybdos, meanin leid, syne its ores wur confused wi leid ores.[4] Molybdenum minerals hae been kent intae prehistory, but the element wis discovered (in the sense o differentiatin it as a new entity frae the mineral sauts o ither metals) in 1778 bi Carl Wilhelm Scheele. The metal wis first isolatit in 1781 bi Peter Jacob Hjelm.

Molybdenum daes nae occur naiturally as a free metal on Yird, but rather in various oxidation states in minerals. The free element, which is a sillery metal wi a gray cast, haes the saxt-heichest meltin pynt o ony element. It readily furms haird, stable carbides in alloys, an for this reason maist o warld production o the element (aboot 80%) is in makin mony types o steel alloys, includin heich strength alloys an superalloys.

Maist molybdenum compounds hae law solubility in watter, but the molybdate ion MoO2−
4
is soluble an furms when molybdenum-containin minerals are in contact wi oxygen an watter. Industrially, molybdenum compoonds (aboot 14% o warld production o the element) are uised in high-pressure an heich-temperatur applications, as pigments an catalysts.

Molybdenum-containin enzymes are bi far the maist common catalysts uised bi some bacteria tae break the chemical bond in atmospheric molecular nitrogen, allaein biological nitrogen fixation. At least 50 molybdenum-containin enzymes are nou kent in bacteria an ainimals, altho anly bacterial an cyanobacterial enzymes are involved in nitrogen fixation, an these nitrogenases contain molybdenum in a different furm frae the rest. Owin tae the diverse functions o the various ither types o molybdenum enzymes, molybdenum is a required element for life in aw heicher organisms (eukaryotes), tho nae in aw bacteria.

References[eedit | eedit soorce]

  1. "Molybdenum: molybdenum(I) fluoride compound data". OpenMOPAC.net. Retrieved 2007-12-10. 
  2. Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press.
  3. A. Lindemann, J. Blumm (2009). "Measurement of the Thermophysical Properties of Pure Molybdenum". 17th Plansee Seminar 3. 
  4. Lide, David R., ed. (1994). "Molybdenum". CRC Handbook of Chemistry and Physics 4. Chemical Rubber Publishing Company. p. 18. ISBN 0-8493-0474-1.