Magnesium is one of the alkaline-earth metals of main group IIa in the periodic table.
Magnesium is a grayish-white metal. Normally magnesium is covered with a layer of oxide, MgO,
that protects magnesium from air and water. Magnesium is an important element for plant and
animal life. Chlorophylls depend greatly on it.Sir Humphrey Davy discovered magnesium in 1775
at England. It was dicovered when he evaporated magnesium amalgam by mixing a moist
magnesia and mercuric oxide. The meaning of the name comes from a Greek word Magnesia.
Properties of pure magnesium:
Atomic number 12
Atomic mass 24.31
Colour Silvery grey metal
Density1.738 g.cm -3 at 20C
1.58 g.cm-3 at 650RC (1)
Melting point 650C
Boiling point 1103C
Crystal structure close-packed hexagonal
Heat of combustion25020 kJ.kg -1
Heat of fusion368 kJ.kg-1
Heat of vaporisation5272 kJ.kg-1
Specific heat1025 J.K -1.kg at 20C
Vapour pressure 20 Pa at 527C(s)
360 Pa at 650C (1)
1400 Pa at 727C
Viscosity 1.25 cp at 650C (1)
The magnesium element has the atomic number of 12 and atomic weight of 24.3050. Its
symbol is Mg. The group number that mg is in is group 2a. Its electronic configuration of
Standard state: solid at 298 K
Colour: silvery white
Density of solid at ambient temperature/kg m-3: 1738
Molar volume/cm3: 14.00
Table on isotopes:
Nominal mass Accurate mass%natural abundance
24Mg23.9850423 (8)78.99 (3)
25Mg24.9858374 (8)10.00 (1)
26Mg25.9825937 (8)11.01 (2)
Magnesium is the 6th most abundant element metal on the surface of the earth at about 2.5%
of its composition. Sea water contains 0.13% Mg and some facilities use the magnesium for the
production of magnesium metal. This happens when the precipitation of other salts leave a
magnesium-rich brine. Other sources are dolomite ((CaMg)CO3) and magnesite (MgCO3).
Magnesite also produces magnesium oxide which are used for the making of refractories.
Magnesium oxide, MgO, is the second most common compounds in the earth’s crust, second
only to silicon dioxide, or beach sand. In seawater, the magnesium compound is magnesium
chloride, MgCl2. The chloride is taken from seawater and is used in the electrolysis process to
manufacture magnesium metal. When seawater is not available, magesium can be found from
minerals such as dolomite (CaCO3.MgCO3) and carnallite (KCl.MgCl2.6H2O).
Magnesium is an active metal. Magnesium burns easily in air, making a bright white light.
Magnesium is an important element for improving the working characteristics of aluminum and
zinc. It makes them easier to roll and machine. Magnesium is also flammable at temperatures
characteristic of burning gasoline 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.
Magnesium compunds 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 for as lining for glass.
-magnesium peroxide, Mg2O2, which is used as a bleach for dyes and silks.