magnesium

Magnesium

Name:Magnesium

Symbol:Mg

Atomic Number:12

Atomic Mass:24.3050

Density: 14.00 g/cm^3

Melting Point:650 �C

Boiling Point:1090 �C

Group Number:2

Group Name:Alkaline Earth Metals

Standard State:solid at room temperature

Color:silvery white

Classification:Metallic

Availability:magnesium is available in several forms including chips,

granules, powder, rod, foil, sheet, rod, turnings, and ribbon.

Magnesium is a grayish-white, fairly tough metal.

magnesium rods

Magnesium is the eighth most abundant element in the earth's crust

although not found in it's elemental form. It is a Group 2

element.Group 2 elements are called alkaline earth metals.

Magnesium tarnishes slightly in air, and finely divided magnesium

readily ignites upon heating in air and burns with a dazzling white

flame. Normally magnesium is coated with a layer of oxide, MgO, that

protects magnesium from air and water.

Magnesium metal burns with a very bright light. The picture above

shows the color arising from adding magnesium powder to a burning

mixture of potassium chlorate and sucrose. Do not attempt this

reaction unless are a professionally qualified chemist and you have

carried out a legally satisfactory hazard assessment.

Magnesium is an important element for plant and animal life.

Chlorophylls are porphyrins based upon magnesium. The adult human

daily requirement of magnesium is about 0.3 g day^-1.

Isolation

Magnesium can be made commercially by several processes and would not

normally be made in the laboratory because of its ready availability.

There are massive amounts of magnesium in seawater. This can be

recovered as magnesium chloride, MgCl[2] through reaction with calcium

oxide, CaO.

CaO + H[2]O -> Ca^2+ + 2OH^-

Mg^2+ + 2OH^- -> Mg(OH)[2]

Mg(OH)[2] + 2HCl -> MgCl[2] + 2H[2]O

Electrolysis of hot molten MgCl[2] affords magnesium as a liquid whih

is poured off and chlorine gas.

cathode: Mg^2+(l) + 2e^- -> Mg anode: Cl^-(l) -> ^1/[2]Cl[2] (g) + e^-

The other methos used to produce magnesium is non electrolytic and

involves dolomite, [MgCa(CO[3])[2]], an important magnesium mineral.

This is "calcined" by heating to form calcined dolomite, MgO.CaO, and

this reacted with ferrosilicon alloy.

2[MgO*CaO] + FeSi -> 2Mg + Ca[2]SiO[4] + Fe