The oxide of molybdenum was first isolated by the Swedish chemist, Carl Wilhelm Scheele, in 1778, and the metal itself was first isolated by his compatriot and colleague, Peter Jacob Hjelm, in 1782.
In 1781, Scheele succeeded also in isolating the oxide of tungsten, from the mineral now known as scheelite. The metal was isolated two years later by the Spanish brothers, Juan Jose dæElhuyar and Fuasto dæElhuyar.
The oxide of chromium was discovered in 1797 by the French scientist, Louis Nicolas Vauquelin, who isolated the metal itself the following year.
