Molybdenum

Molybdenum is a chemical element with the symbol Mo and atomic number 42. It is a silvery-gray transition metal with a very high melting point: Los Alamos National Laboratory lists it at 2,896 kelvin. Its name derives from the Greek molybdos, meaning lead, reflecting the historical confusion between molybdenite and lead ores.

The mineral molybdenite was long mistaken for graphite or a lead mineral. In 1778, Swedish chemist Carl Wilhelm Scheele showed that it was distinct and contained a previously unknown element. Peter Jacob Hjelm isolated the metal in 1781. Today molybdenum is obtained chiefly from molybdenite; it can also be recovered as a by-product of copper and tungsten mining.

Molybdenum is widely used as an alloying element. Added to steel and stainless steel, it can improve strength, hardness, and resistance to corrosion and heat; it is also used in nickel alloys and in components exposed to demanding temperatures. Molybdenum disulfide is used as a solid lubricant, and other molybdenum compounds have uses as catalysts and pigments.

Molybdenum is required in small amounts by plants and animals. It forms part of enzymes, including nitrogenase in certain nitrogen-fixing bacteria, which enables atmospheric nitrogen to be converted into compounds usable by living organisms. This biological role is distinct from the industrial uses of the metal.