Molybdenum

Molybdenum (chemical symbol: Mo) is a transition metal with atomic number 42. It is a silvery metal that is extremely hard and heat-resistant. Its melting point is exceptionally high compared to common metals, which is why it is used in equipment exposed to high temperatures.

In nature, molybdenum is rarely found as a pure metal but occurs in various ores. The principal ore extracted is molybdenite, a compound consisting of molybdenum and sulfur. It is most often found as a by-product in copper mines.

History of discovery

The name molybdenum derives from a Greek word meaning lead, because molybdenite and graphite were long confused with each other due to their similar appearance and luster. In the 18th century, molybdenite was established to be distinct from lead, and the new element was identified. Pure metal was isolated shortly afterward.

Chemical properties

Molybdenum exhibits various oxidation states, the most common being +4 and +6. Important compounds include molybdenum trioxide and molybdenum disulfide. Molybdenum disulfide is used as a solid lubricant because of its layered structure.

Industrial applications

The largest use of molybdenum is in strengthening steel alloys. Adding molybdenum increases hardness, strength, and corrosion resistance, particularly in stainless steels and those used in oil pipelines. It is also used as a catalyst in oil refining to remove sulfur from petroleum.

Biological role

Molybdenum is an essential trace element for most organisms. It forms the active site of several enzymes, including those involved in bacterial nitrogen fixation, the process by which bacteria convert atmospheric nitrogen into a form usable by plants. In humans, it is present in enzymes involved in sulfur compound metabolism. Deficiency in human diet is rare.