| Magnesium - Mg
CAS: 7439-95-4 Description: Grayish-white metal Classification: Alkaline Earth Date of Discovery: 1808 Discoverer: Sir Humphrey Davy Name Origin: Magnesia, district in Thessaly |
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Atomic Number: 12
Number of Neutrons: 12 Atomic Mass: 24.3050(6) amu Melting Point: 650 °C Boiling Point: 1090 °C Density (293 K): 1.738 g/cm3 Atomic volume: 13.97 cm3/mol Electrical resistivity: 0.226 10-6/cm 
Thermal conductivity: 1.56 W/cmK Enthalpy of atomization: 148.53 kJ/mol Enthalpy of vaporization: 127.40 kJ/mol Enthalpy of fusion: 8.954 kJ/mol Specific heat capacity: 1.02 J/gK |
Energy levels: 2-8-2
Electron configuration: [Ne]3s2 Crystal Structure: Hexagonal Atomic radius: 1.72 Å Covalent radius: 1.36 Å Oxidation States: +2 Electronegativity, Pauling: 1.31 Electron affinity: not stable First ionization energy: 7.646 eV 2nd ionization energy: 15.035 eV 3rd ionization energy: 80.143 eV Polarizability: 10.6 10-24cm3 |
| Isotope | Natural Abundance | Atomic Mass | Half-life | Decay Mode | Spin |
| 20Mg | 20.01886 | 0.1 s |  +, p |
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| 21Mg | 21.01171 | 122 ms | +, p |
5/2+ | |
| 22Mg | 21.999574 | 3.86 s | + |
0+ | |
| 23Mg | 22.994125 | 11.32 s | + |
3/2+ | |
| 24Mg | 78.99(3) | 23.9850419 | Stable | 0+ | |
| 25Mg | 10.00(1) | 24.9858370 | Stable- | 5/2+ | |
| 26Mg | 11.01(2) | 25.9825930 | Stable | 0+ | |
| 27Mg | 26.9843407 | 9.45 m | - |
1/2+ | |
| 28Mg | 27.983877 | 20.9 h | - |
0+ | |
| 29Mg | 28.98855 | 1.3 s | - |
3/2+ | |
| 30Mg | 29.99046 | 0.32 s | - |
0+ | |
| 31Mg | 30.99655 | 0.24 s | - |
(3/2+) | |
| 32Mg | 31.9992 | 0.12 s | - |
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| 33Mg | 33.0056 | 0.09 s | - |
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| 34Mg | 34.0091 | .02 s | - |
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Compounds of magnesium have long been known. Black recognized magnesium as an element in 1755. It was isolated by Davy in 1808, and prepared in coherent form by Bussy in 1831. Magnesium is the eighth most abundant element in the earth's crust. It does not occur uncombined, but is found in large deposits in the form of magnesite (MgCO3), dolomite [CaMg(CO3)2], and other minerals. The metal is now principally obtained in the U.S. by electrolysis of fused magnesium chloride derived from brines, wells, and sea water. Magnesium is a light, silvery-white, and fairly tough metal. It
tarnishes slightly in air, and finely divided magnesium readily ignites upon heating in air and burns with a dazzling white flame. It is used in flashlight photography, flares, and pyrotechnics, including incendiary bombs. It is one third lighter than aluminum,
and in alloys is essential for airplane and missile contruction. The metal improves the mechanical, fabrication, and welding characteristics of aluminum when used as an alloying agent. Magnesium is used in producing nodular graphite in cast iron, and is used as an additive to conventional propellants. It is also used as a reducing agent in the production of pure uranium and other metals from their salts. The hydroxide (milk of magnesia), chloride, sulfate (Epsom salts), and citrate are used in medicine.
Dead-burned magnesite is employed for refractory purposes such as brick and liners in furnaces and converters. Organic magnesium compounds (Grignard's reagents) are important. Magnesium is an important element in both plant and animal life. Chlorophylls are
magnesium-centered porphyrins. The adult daily requirement of magnesium is aoout 300 mg/day, but this is affected by various factors. Great care should be taken in handling magnesium metal, especially in the finely divided state, as serious fires can occur.
Water should not be used on burning magnesium or on magnesium fires. Natural magnesium contains three isotopes. Twelve other isotopes are recognized.
LINKS: Dietary Magnesium and Asthma Haley's MO Cabinet Magnesium Alloy Corporation Magnesium Deficiency Magnesium, in Your Drinking Water! Magnesium May Stave off Cerebral Palsy Magnesium the Beautiful Minerals Containing Magnesium Return
Sources for the information on this website include: Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998. |
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