PTL:Molybdenum
From ChemEd Collaborative
Molybdenum is a transition metal in Group VIB (Group 6) and the 5th period. It has oxidation numbers ranging from 0 to +6, with +6 being common and +2, +3, +4, and +5 less so. Other members of Group VIB are chromium (Cr) and tungsten (W).
Contents |
Discovered
The elements of Group VIB were all discovered in a 20 year period at the end of the 18th century. In 1778 the Swedish chemist Scheele produced MoO3 from molybdenite (MoS2), and P.J. Hjelm isolated the metal from the oxide several years later by reducing the oxide with charcoal.
MoO3(s) + 3 C(s) 
Mo(s) + 3 CO(g)
Name
The name is derived from the Greek word for lead as molybdenite was often confused with lead and graphite.
Characteristics
Chromium is the most abundant of the Group VIB metals in the earth's crust (126 ppm), while molybdenum and tungsten both have abundances of only about 1.2 ppm.
Molybdenum metal is silvery white and very hard, although less hard and more ductile than tungsten. Only tungsten and tantalum have higher melting points.
Found
Molybdenum does not occur in native form. Rather, it is isolated chiefly from the mineral molybdenite, MoS2, but a secondary source is the beautiful yellow mineral wulfenite, PbMoO4.
Uses
More than 80% of the molybdenum produced is used in [alloys], chiefly with chromium, nickel and iron. The Hastelloys® are Ni-Mo alloys with superior resistance to corrosion.
Molybdenum alloys are also used as [filaments in burners] and its compounds have found use as catalysts. The structure of MoS2 shows it to be layered material, much like graphite, so it has found use as a [lubricant], especially at high temperatures where oils would decompose.
Emission Spectra
This is the emission spectra for Molybdenum.
