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This is magnesium.

Symbol Mg
Atomic number 12
Atomic mass 24.305 amu

Magnesium, discovered in 1775, is a chemically active metal. Finely ground or powdered magnesium burns easily in air, producing a brilliant white light.

Magnesium is the eighth most abundant element. Magnesium oxide, MgO, is the second most common compounds in the earth's crust, second only to silicon dioxide, or ordinary beach sand.

Distinguishing properties

Magnesium is an important alloying agent for improving the working characteristics of aluminum and zinc. It makes them easier to roll, extrude, weld and machine. Magnesium is also flammable at temperatures characteristic of burning gasoline and other petrochemicals, so its use as a structural metal is limited. Insoluble magnesium carbonate and magnesium sulfate, together with insoluble calcium compounds occur in "hard" water. These compounds are observed as scales in pipes and boilers. However, magnesium is an important catalyst in organic reactions.


In seawater, the principal magnesium compound is magnesium chloride, MgCl2. The chloride is obtained directly from seawater and is chiefly used in the electrolysis process to manufacture magnesium metal. When seawater is not conveniently available, magnesium can be recovered from minerals such as dolomite (CaCO3.MgCO3) and carnallite (KCl.MgCl2.6H2O).


Magnesium a metal that is essential to good health. A deficiency in man can have the same effect as alcoholism. Magnesium hydroxide, Mg(OH)2, is used in medicine as an antacid.

Common compounds

Other magnesium compounds include:

  • magnesium chloride, MgCl2, which is used in the preparation of cotton fabrics.
  • magnesium bicarbonate,Mg(HCO3)2, which is produced in solution when water containing carbon dioxide dissolves magnesium carbonate. It is a cause of hardness in water.
  • magnesium oxide, MgO, which is used as a refractory lining for metal, glass, and cement furnaces.
  • magnesium peroxide, Mg2O2, which is used as a bleach for dyes and silks.
  • magnesium sulfate, MgSO4, which is used as a purgative drug and as an antidote for barium and barbiturate poisoning. It is also used in dyeing and sizing of textiles, in man-made fibre production, and as a source of magnesium in fertilizers. One hydrated form, MgSO4.7H2O, is known as Epsom salt.

See also

Periodic table of the elements