Magnesium
Magnesium ( /mæɡˈniːziəm/ mag-NEE-zee-əm) is a chemical element with the symbol Mg, atomic number 12 and common oxidation state +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust, where it constitutes about 2% by mass, and ninth in the known universe as a whole.[6] This preponderance of magnesium is related to the fact that it is easily built up in supernova stars from a sequential addition of three helium nuclei to carbon (which in turn is made from three helium nuclei). Magnesium ion's high solubility in water helps ensure that it is the third most abundant element dissolved in seawater.[7]
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| General properties | |||||||||||||||||||||
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| Pronunciation | /mæɡˈniːziəm/ | ||||||||||||||||||||
| Appearance | shiny grey solid | ||||||||||||||||||||
| Standard atomic weight (Ar, standard) | [24.304, 24.307][1] | ||||||||||||||||||||
| Magnesium in the periodic table | |||||||||||||||||||||
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| Atomic number (Z) | 12 | ||||||||||||||||||||
| Group | group 2 (alkaline earth metals) | ||||||||||||||||||||
| Period | period 3 | ||||||||||||||||||||
| Block | s-block | ||||||||||||||||||||
| Element category | alkaline earth metal | ||||||||||||||||||||
| Electron configuration | [Ne] 3s2 | ||||||||||||||||||||
Electrons per shell | 2, 8, 2 | ||||||||||||||||||||
| Physical properties | |||||||||||||||||||||
| Phase at STP | Mg: Solid | ||||||||||||||||||||
| Melting point | 923 K (650 °C, 1202 °F) | ||||||||||||||||||||
| Boiling point | 1363 K (1091 °C, 1994 °F) | ||||||||||||||||||||
| Density (near r.t.) | 1.738 g/cm3 | ||||||||||||||||||||
| when liquid (at m.p.) | 1.584 g/cm3 | ||||||||||||||||||||
| Heat of fusion | 8.48 kJ/mol | ||||||||||||||||||||
| Heat of vaporization | 128 kJ/mol | ||||||||||||||||||||
| Molar heat capacity | 24.869 J/(mol·K) | ||||||||||||||||||||
Vapor pressure
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| Atomic properties | |||||||||||||||||||||
| Oxidation states | +1,[2] +2 (a strongly basic oxide) | ||||||||||||||||||||
| Electronegativity | Pauling scale: 1.31 | ||||||||||||||||||||
| Ionization energies |
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| Atomic radius | empirical: 160 pm | ||||||||||||||||||||
| Covalent radius | 141±7 pm | ||||||||||||||||||||
| Van der Waals radius | 173 pm | ||||||||||||||||||||
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| Other properties | |||||||||||||||||||||
| Natural occurrence | Mg: Primordial | ||||||||||||||||||||
| Crystal structure | hexagonal close-packed (hcp) | ||||||||||||||||||||
| Speed of sound thin rod | 4940 m/s (at r.t.) (annealed) | ||||||||||||||||||||
| Thermal expansion | 24.8 µm/(m·K) (at 25 °C) | ||||||||||||||||||||
| Thermal conductivity | 156 W/(m·K) | ||||||||||||||||||||
| Electrical resistivity | 43.9 nΩ·m (at 20 °C) | ||||||||||||||||||||
| Magnetic ordering | paramagnetic | ||||||||||||||||||||
| Magnetic susceptibility | +13.1·10−6 cm3/mol (298 K)[3] | ||||||||||||||||||||
| Young's modulus | 45 GPa | ||||||||||||||||||||
| Shear modulus | 17 GPa | ||||||||||||||||||||
| Bulk modulus | 35.4[4] GPa | ||||||||||||||||||||
| Poisson ratio | 0.290 | ||||||||||||||||||||
| Mohs hardness | 1–2.5 | ||||||||||||||||||||
| Brinell hardness | 44–260 MPa | ||||||||||||||||||||
| CAS Number | 7439-95-4 | ||||||||||||||||||||
| History | |||||||||||||||||||||
| Naming | after Magnesia, Greece | ||||||||||||||||||||
| Discovery | Joseph Black (1755) | ||||||||||||||||||||
| First isolation | Humphry Davy (1808) | ||||||||||||||||||||
| Main isotopes of magnesium | |||||||||||||||||||||
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Magnesium is the 11th most abundant element by mass in the human body. Its ions are essential to all living cells. The ions play a major role in manipulating important biological polyphosphate compounds like ATP, DNA, and RNA. Hundreds of enzymes thus require magnesium ions to function. Magnesium is also the metallic ion at the center of chlorophyll, and is thus a common additive to fertilizers.[8] Magnesium ions are sour to the taste, and in low concentrations help to impart a natural tartness to fresh mineral waters.
The free element (metal) is not found naturally on Earth, as it is highly reactive (though once produced, is coated in a thin layer of oxide (see passivation), which partly masks this reactivity). The free metal burns with a characteristic brilliant white light, making it a useful ingredient in flares. The metal is now mainly obtained by electrolysis of magnesium salts obtained from brine.
Uses
Commercially, the chief use for the metal is as an alloying agent to make aluminium-magnesium alloys, sometimes called "magnalium" or "magnelium". Since magnesium is less dense than aluminium, these alloys are prized for their relative lightness and strength.
Magnesium is used in fireworks to make a brilliant bright light. Another use is to mix it with other metals to make it strong, lightweight alloys such as those used to make bicycle frames.
Magnesium compounds are used medicinally as common laxatives, antacids (i.e., milk of magnesia), and in a number of situations where stabilization of abnormal nerve excitation and blood vessel spasm is required (that is, to treat eclampsia).
Magnesium is used in electronic devices, including: mobile phones, laptop computers, cameras, and other electronic components. Magnesium's low weight, good mechanical and electrical properties are good for these uses.
Magnesium reacted with an alkyl halide gives a Gringard reagent, which is a very useful tool for preparing alcohols.
Magnesium is also used in incendiary bombs, which are bombs that blow up and spread fire everywhere.
Magnesium Media
Magnesium is brittle, and fractures along shear bands when its thickness is reduced by only 10% by cold rolling (top). However, after alloying Mg with 1% Al and 0.1% Ca, its thickness could be reduced by 54% using the same process (bottom).
Magnesium sheets and ingots
An unusual application of magnesium as an illumination source while wakeskating in 1931
The Bugatti Type 57 Aérolithe featured a lightweight body made of Elektron, a trademarked magnesium alloy.
Products made of magnesium: firestarter and shavings, sharpener, magnesium ribbon
Magnesium firestarter (in left hand), used with a pocket knife and flint to create sparks that ignite the shavings
Magnesium block heated with blowtorch to self-combustion, emitting intense white light
Examples of food sources of magnesium (clockwise from top left): bran muffins, pumpkin seeds, barley, buckwheat flour, low-fat vanilla yogurt, trail mix, halibut steaks, garbanzo beans, lima beans, soybeans, and spinach
Related pages
References
- ↑ Meija, J.; Coplen, T. B.; Berglund, M.; Brand, W.A.; De Bièvre, P.; Gröning, M.; Holden, N.E.; Irrgeher, J.; Loss, R.D.; Walczyk, T.; Prohaska, T. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
{{cite journal}}: Unknown parameter|displayauthors=ignored (|display-authors=suggested) (help) - ↑ Bernath, P. F.; Black, J. H.; Brault, J. W. (1985). "The spectrum of magnesium hydride" (PDF). Astrophysical Journal. 298: 375. Bibcode:1985ApJ...298..375B. doi:10.1086/163620.
{{cite journal}}: Unknown parameter|lastauthoramp=ignored (|name-list-style=suggested) (help) - ↑ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
- ↑ K. A. Gschneider, Solid State Phys. 16, 308 (1964)
- ↑ Bernath, P. F.; Black, J. H.; Brault, J. W. (1985). "The spectrum of magnesium hydride" (PDF). Astrophysical Journal. 298: 375. Bibcode:1985ApJ...298..375B. doi:10.1086/163620.
- ↑ Ash, Russell (2005). The Top 10 of Everything 2006: The Ultimate Book of Lists. Dk Pub. ISBN 0756613213. Archived from the original on 2010-02-10. Retrieved 2011-09-26..
- ↑ Anthoni, J Floor (2006). The chemical composition of seawater. http://www.seafriends.org.nz/oceano/seawater.htm#composition.
- ↑ "Magnesium in health".
