Introduction group VIB

Group VIB includes following elements: Chromium - [Cr], Molybdenum - [Mo], Tungsten - [W].

The discoveries of these elements span a period of about 20 y at the end of the eighteenth century. In 1778 the famous Swedish chemist C. W. Scheele produced from the mineral molybdenite (MoS2) the oxide of a new element, thereby distinguishing the mineral from graphite with which it had hitherto been thought to be identical. Molybdenum metal was isolated 3 or 4 y later by P. J. Hjelm by heating the oxide with charcoal.

In 1781 Scheele, and also T. Bergman, isolated another new oxide, this time from the mineral now known as scheelite (CaWO4) but then called “tungsten” (Swedish tung sten, heavy stone). Two years later the Spanish brothers J. J. and F. d’Elhuyar showed that the same oxide was a constituent of the mineral wolframite and reduced it to the metal by heating with charcoal. The name “wolfram”, from which the symbol of the element is derived, is still widely used in the German literature and is recommended by IUPAC, but the allowed alternative “tungsten” is used in the Englishspeaking world.

Finally, in 1797, the Frenchman L. N. Vauquelin discovered the oxide of a new element in a Siberian mineral, now known as crocoite (PbCrO4), and in the following year isolated the metal itself by charcoal reduction. This was subsequently named chromium (Greek - chroma, colour) because of the variety of colours found in its compounds. Since their discoveries the metals and their compounds have become vitally important in many industries and, as one of the biologically active transition elements, molybdenum has been the subject of a great deal of attention in recent years.