Periodic Table ~ molybdenum ~ Element ~ CAS 7439-98-7

molybdenum

Name	molybdenum
Symbol	Mo
Atomic Weight	95.94
Atomic Number	42
CAS ID	7439-98-7
Group Number	6
Group Name	(none)
Period Number	5
Origin of Name	Greek, molybdos = "lead"
Year Discovered	1781
Discovery Credits	Isolated by P. J. Hjelm at Uppsala, Sweden
Class	Metallic
Color	Gray Metallic
Standard State	Solid at 77 F & 298 K
Description	Metal is lustrous, silvery, and fairly soft when pure. Usually obtained as gray powder. Used in alloys, electrodes, catalysts, and as the sulfide, lubricants. Diagnostic tests: On charcoal molybdenum sulfide gives near the assay a copper-red stain in oxidizing flame and white oxide further away. On plaster, mixed with KI, gives a deep ultramarine blue color after heating with the flame. Bead tests using sodium phosphate (Na₃PO₄) gives a yellowish green color (hot) and nearly colorless (cold), the reducing flame color is a fine green. Molybdates (MoO₄^2-) are tested by adding powdered sample to a dry test tube with a scrap of paper, adding a few drops of water and an equal amount of concentrated H₂SO₄. The mixture is carefully heated until the acid fumes. Cool or slowly add water and the solution will assume a deep blue color.