magnesium n. a light silvery-white metallic element of the alkaline earth series, occurring principally in magnesite, dolomite and carnallite: used in light structural alloys. Symbol: Mg; atomic number: 12; atomic weight: 24.312; valency: 2; relative density: 1.738; melting point: 651°C; boiling point: 1107°C; crystal structure: close-packed hexagonal (a=3.2030 c= 5.2002).
Magnesium is the lightest of all structural metals: 75% lighter in weight than steel and 33% lighter than aluminum. The English scientist Sir Humphry Davy first isolated this element in 1808 but it was not until 1852 that German chemist Robert Bunsen demonstrated that magnesium metal could be isolated by electrolysis of fused anhydrous magnesium chloride, with magnesium released at the cathode and chlorine at the anode of the cell.
Magnesium is used today in a diverse range of markets and applications that benefit from unique physical and mechanical properties of the element and its alloys. World production of magnesium totals about 850,000 tons per year, with the quantity increasing annually as magnesium alloys are increasingly used in the aviation and automotive industries to reduce weight, increase fuel efficiency and reduce greenhouse gas emissions.