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12 Mg 24.3050(6)

Magnesium

Alkaline earth metal
Symbol Mg
Atomic Number 12
Atomic Weight 24.3050(6)
CAS Registry ID 7439-95-4
Group Name Alkaline earth metal
Period Number 3
Block s-block
State at STP Solid

Description

Sample of Magnesium ⌕ Enlarge Image

Magnesium is an alkaline earth metal with an atomic weight of 24.3050. In its natural state, magnesium is a silvery white solid; it has a melting point of 1202 °F, and a boiling point of 1994 °F. Magnesium is a flammable metal that reacts with water. Common uses of magnesium include: mixed with other compounds for light alloys used in aircraft, car engines, and missiles, as a reducing agent for uranium production, and for medicinal purposes in the form of milk of magnesia and Epsom salts.

Isolation

Magnesium is not found free in nature, and there are a variety of processes used to isolate pure magnesium from other compounds.

Magnesium ⌕ Enlarge Image

Magnesium is the 3rd most abundant element found in sea water, and so one of the main isolation procedures used to isolate magnesium use sea water as a source. The first step of this isolation process involves adding calcium carbonate to the sea water to form a precipitate of magnesium carbonate. The magnesium carbonate is not soluble in water, so it is filtered out and then reacted with hydrochloric acid. The second reaction with hydrochloric acid produces magnesium chloride. Pure magnesium is separated from the magnesium chloride compound through electrolysis.

Another isolation magnesium procedure uses dolomite. Dolomite is a sedimentary rock/mineral that is composed of calcium magnesium carbonate; therefore, dolomite is an important resource of pure magnesium. In this isolation process, the dolomite is heated to form calcined dolomite. The calcined dolomite is then reacted with ferrosilicon allow. The final distillation step is used to remove pure magnesium from the end products of this reaction.

General

NameMagnesium
SymbolMg
Number12
Chemical seriesAlkaline earth metal
Group2
Period3
Blocks
Appearancesilvery white
Standard atomic weight24.3050(6) g·mol⁻¹
Electron configuration[Ne] 3s2
Electrons per shell2, 8, 2

Atomic Properties

Crystal structurehexagonal
Oxidation states2 (strongly basic oxide)
Electronegativity1.31 (Pauling scale)
Ionization energies1st: 737.7 kJ·mol−1
2nd: 1450.7 kJ·mol−1
3rd: 7732.7 kJ·mol−1
Atomic radius150 pm
Atomic radius (calc.)145 pm
Covalent radius130 pm
Van der Waals radius173 pm

Physical Properties

Phasesolid
Density (near r.t.)1.738 g·cm−3
Liquid density at m.p.1.584 g·cm−3
Melting point923 K (650 °C, 1202 °F)
Boiling point1363 K (1090 °C, 1994 °F)
Critical point
Heat of fusion8.48 kJ·mol−1
Heat of vaporization128 kJ·mol−1
Heat capacity(25 °C) 24.869 J·mol−1·K−1

Miscellaneous

Magnetic orderingparamagnetic
Electrical resistivity(20 °C) 43.9 nΩ·m
Thermal conductivity(300 K) 156 W·m−1·K−1
Thermal expansion(25 °C) 24.8 µm·m−1·K−1
Speed of sound (thin rod)(r.t.) (annealed) 4940 m·s−1
Young's modulus45 GPa
Shear modulus17 GPa
Bulk modulus45 GPa
Poisson ratio0.29
Mohs hardness2.5
Vickers hardness
Brinell hardness260 MPa