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Molybdenum (Mo)

Molybdenum is a chemical element of the periodic table with chemical symbol Mo and atomic number 42 with an atomic weight of 95.951 u and is classed as transition metal and is part of group 6 (chromium group). Molybdenum is solid at room temperature.

Molybdenum in the periodic table

Atomic number42
Group6 (Chromium group)
ClassificationTransition Metal
AppearanceGray metallic
Color Gray
Number of protons42 p+
Number of neutrons54 n0
Number of electrons42 e-
From Wikipedia, the free encyclopediaMolybdenum is a chemical element with 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. 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.

Physical properties

Phase at STPSolid
Density10.28 g/cm3
Atomic weight95.951 u

Thermal properties

Melting point2896 K
2622.85 °C
4753.13 °F
Boiling point4912 K
4638.85 °C
8381.93 °F
Heat of vaporization590.4 kJ/mol

Atomic properties

Electronegativity (Pauling Scale)2.16
Electron affinity72.1 kJ/mol
Oxidation states−4, −2, −1, 0, +1, +2, +3, +4, +5, +6
(a strongly acidic oxide)
Ionization energies
  1. 684.3 kJ/mol
  2. 1560 kJ/mol
  3. 2618 kJ/mol
  4. 4480 kJ/mol
  5. 5257 kJ/mol
  6. 6640.8 kJ/mol
  7. 12125 kJ/mol
  8. 13860 kJ/mol
  9. 15835 kJ/mol
  10. 17980 kJ/mol
  11. 20190 kJ/mol
  12. 22219 kJ/mol
  13. 26930 kJ/mol
  14. 29196 kJ/mol
  15. 52490 kJ/mol
  16. 55000 kJ/mol
  17. 61400 kJ/mol
  18. 67700 kJ/mol
  19. 74000 kJ/mol
  20. 80400 kJ/mol
  21. 87000 kJ/mol
  22. 93400 kJ/mol
  23. 98420 kJ/mol
  24. 104400 kJ/mol
  25. 121900 kJ/mol
  26. 127700 kJ/mol
  27. 133800 kJ/mol
  28. 139800 kJ/mol
  29. 148100 kJ/mol
  30. 154500 kJ/mol

Electron configuration for molybdenum

Electron configuration
Shorthand configuration
[Kr] 4d5 5s1
Electron configuration
Full configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d5 5s1
Electron configuration chart
Electrons per shell2, 8, 18, 13, 1
Valence electrons 6
Valency electrons 2,3,4,5,6
Bohr model
MolybdenumElectron shell for Molybdenum, created by Injosoft ABMo
Figure: Shell diagram of Molybdenum (Mo) atom.
Orbital Diagram

The history of Molybdenum

DiscoveryCarl Wilhelm Scheele (1778)
First isolationPeter Jacob Hjelm (1781)
Discovery of molybdenum
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. ca. 1330), that art was never employed widely and was later lost. In the West in 1754, Bengt Andersson Qvist examined a sample of molybdenite and determined that it did not contain lead and thus was not galena. By 1778 Swedish chemist Carl Wilhelm Scheele stated firmly that molybdena was (indeed) neither galena nor graphite. Instead, Scheele correctly proposed that molybdena was an ore of a distinct new element, named molybdenum for the mineral in which it resided, and from which it might be isolated. Peter Jacob Hjelm successfully isolated molybdenum using carbon and linseed oil in 1781.


List of unique identifiers for Molybdenum in various chemical registry databases
CAS Number7439-98-7
ChemSpider ID22374
EC number231-107-2
PubChem CID Number23932