Magnesium

Magnesium is a chemical element in the periodic table that has the symbol Mg and atomic number 12. Magnesium is the eigth most abundent element and constitutes about 2% of the Earth's crust, and it is the third most plentiful element dissolved in seawater. This alkaline earth metal is primarily used as an alloying agent to make aluminum-magnesium alloys.

Properties

General
Name	Magnesium
Symbol	Mg
Series	alkaline earth metals
Group, Period, Block	2 (IIA), 3, s
Relative abundance	8.18 (log10) Earth
Density at 293 K	1738 kg/m3
Hardness (Mohs)	2.5
Appearance	silvery white
Atomic
Atomic number	12
Atomic weight	24.305 amu
Atomic radius	150 pm (145 pm calc.)
Covalent radius	130 pm
van der Waals radius	173 pm
Electron configuration	[Ne]3s2
e- 's per energy level	2, 8, 2
Oxidation states	2
Crystal structure	Hexagonal
Physical
State of matter at STP	solid
Melting point at 1 atm.	923 K (1202 °F)
Boiling point at 1 atm.	1363 K (1994 °F)
Molar volume	14.00 ×10-3 m3/mol
Specific gravity	1.378
Heat of vaporization	127.4 kJ/mol
Heat of fusion	8.954 kJ/mol
Vapor pressure	361 Pa at 923 K
Velocity of sound	4602 m/s
Other
Electronegativity	1.31 (Pauling scale)
Specific heat capacity	1020 J/kgK
Electrical conductivity	2.17 × 107 S/m
Thermal conductivity	156 W/m-K
1st ionization potential	737.7 kJ/mol
2nd ionization potential	1450.7 kJ/mol
3rd ionization potential	7732.7 kJ/mol
Isotopic
iso NA half-life DM DE MeV DP 24Mg 78.99% Mg is stable with 12 neutrons 25Mg 10% Mg is stable with 13 neutrons 26Mg 11.01% Mg is stable with 14 neutrons
SI units & STP values used where possible.

Notable Characteristics
Magnesium is a fairly strong, silvery-white, light-weight metal (one third lighter than aluminum) that slightly tarnishes when exposed to air. In a powder, this metal heats and ignites when exposed to air and burns with a white flame. It is difficult to ignite in bulk, though it is easy to light if it is shaved in to thin strips.

Uses
Magnesium compounds, primarily magnesium oxide, are used mainly as refractory material in furnace linings for producing iron and steel, nonferrous metals, glass, and cement. Magnesium oxide and other compounds also are used in agricultural, chemical, and construction industries. Magnesium metal's principal use is as an alloying addition to aluminum, and these aluminum-magnesium alloys are used mainly for beverage cans. Magnesium alloys also are used as structural components of automobiles and machinery. Magnesium also is used to remove sulfur from iron and steel.

Other uses include:

• Magnesium, like aluminum, is strong and light, so it is often used in high grade car wheels, called "mag wheels."
• Combined in alloys this metal is essential for airplane and missile construction.
• When used as an alloying agent, this metal improves the mechanical, fabrication, and welding characteristics of aluminum.
• Additive agent for conventional propellants and used in producing nodular graphite in cast iron.
• Reducing agent for the production of pure uranium and other metals from their salts.
• Its hydroxide is used in milk of magnesia, its chloride and sulfate in Epsom salts, and its citrates are used in medicine.
• Dead-burned magnesite is employed for refractory purposes such as brick and liners in furnaces and converters.
• Magnesium is also flammable, burning at a temperature of (4000^oF?).
• The extremely high temperature at which magnesium burns makes it a handy tool for starting emergency fires during outdoor recreation.
• Other uses include flashlight photography, flares, and pyrotechnics, including incendiary bombs.

Compounds
Organic magnesium is important in both plant and animal life. Chlorophylls are magnesium-centered perphyrins. The adult daily nutritional requirement, which is affected by various factors include weight and size, is about 300 mg/day.

History
The named originates from the Greek word for a district in Thessaly called Magnesia. Joseph Black in England recognized magnesium as being an element in 1755, Sir Humphrey Davey electrolytically isolated pure magnesium metal in 1808 from a mix of magnesia and HgO and AA Bussy prepared it in coherent form in 1831. Magnesium is the eighth most abundant element in the earth's crust. It is a rare earth element and therefore does not occur uncombined with other elements. It is found in large deposits of magnesite, dolomite, and other minerals.

Sources
In the United States this metal is principally obtained by electrolysis of fused magnesium chloride from brines, wells, and sea water. Although magnesium is found in over 60 minerals, only dolomite, magnesite, brucite, carnallite, and olivine are of commercial importance.

Isotopes
Magnesium-26 is a stable isotope that has found application in isotopic geology, similar to that of aluminum. ²⁶Mg is a radiogenic daughter product of ²⁶Al (half -life = 0.72x106 yr). Large enrichments of stable ²⁶Mg have been observed in the Ca-Al-rich inclusions of some carbonaceous chondrite meteorites. The anomalous abundance of ²⁶Mg is attributed to the decay of its parent ²⁶Al in the inclusions. Therefore, the meteorite must have formed in the solar nebula before the ²⁶Al had decayed. Hence, these fragments are among the oldest objects in the solar system and have preserved information about its earliest history.

It is conventional to plot ²⁶Mg/²⁴Mg against an Al/Mg ratio. In an isochron plot, the Al/Mg ratio plotted is ²⁷Al/²⁴Mg. The slope of the isochron has no age significance, but indicates the initial ²⁶Al/²⁷Al ratio in the sample at the time when the systems were separated from a common reservoir.

Precautions
Megnesium metal is highly flammable in its pure form, especially when it is a powder.
Magnesium metal quickly reacts exothermically upon contact with air or water and should be handeld with care. Water should not be used to extinguish magnesium fires.

Sources and external links:
Los Alamos National Laboratory - Magnesium
WebElements.com - Magnesium
EnvironmentalChemistry.com - Magnesium
Schenectady County - Magnesium