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| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
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magnesium (Mg)
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Earth's oceans contain an estimated trillion trillions tons of magnesium, and this is the source of much of the 300,000 tons produced annually.
Magnesium was recognized as an element by Joseph Black of Edinburgh in 1775 and first isolated as a metal by Humphry Davy in 1808. It is named after Magnesia, a district of Thessaly in Greece, where it was first found.
| atomic number | 12 |
| relative atomic mass | 24.305 |
| electron configuration | 1s22s22p63s2 |
| melting point | 651 °C (1,204 °F) |
| boiling point | 1,107 °C (2,205 °F) |
| relative density | 1.74 |
| first ionization energy | 737.1 kJ/mol |
| second ionization energy | 1,451 kJ/mol |
| second ionization energy | 1,451 kJ/mol |
| atomic radius | 160 pm |
| ionic radius | 66 pm |
Chemistry of magnesium
Magnesium forms a wide range of ionic compounds. Some common magnesium compounds include milk of magnesia, which is a suspension of magnesium hydroxide and epson salts, which is magnesium sulfate hepahydrate. The ionic compounds of magnesium generally tend to be more soluble than the heavier members of the group. Magnesium can also form covalent bonds with carbon, an example of which is the Grignard reagent phenylmagnesium bromide.
Magnesium is one of the least reactive of the alkaline earth metals. If heated it will react with water to form magnesium hydroxide and hydrogen, but this reaction occurs very slowly. Magnesium ribbon burns in air with a brilliant white light to form magnesium oxide. It will also react with any of the halogens to form the corresponding magnesium halide, and will react with nitrogen to form magnesium nitride at high temperatures. When heated with sulfur, magnesium sulfide is formed. Magnesium reacts readily with acids and displaces the hydrogen from the acid as hydrogen.
Sources and production
The most important sources of magnesium are seawater and dolomite rock, a mixture of calcium and magnesium carbonates. Magnesium is generally obtained by the electrolysis of magnesium halides. In the production of magnesium from seawater the magnesium is precipitated as the hydroxide and converted to the chloride by reaction with hydrochloric acid. The magnesium chloride is recovered by evaporation of the solution, and magnesium metal is obtained by electrolysis of the molten salt.
Magnesium and life
Magnesium is an essential element for all terrestrial life. Humans take in approximately 250-350 milligrams each day (about 4 ounces a year), and we each have about 20 grams (about three-quarters of an ounce) in our bodies, much of it in the bones and teeth. Chlorophyll, the compound responsible for the green color of leaves and for photosynthesis, is a coordination compound containing magnesium.
Dietary sources of magnesium include cereals (especially whole-grain), nuts, soya beans, milk, fish, and meat. Deficiency usually occurs as a result of severe kidney disease, alcohol dependence, an intestinal disorder that impairs the absorption of magnesium and calcium, or prolonged treatment with diuretic drugs or digitalis drugs. Symptoms of deficiency include anxiety, restlessness, tremors, palpitations, and depression. There may also be an increased risk of kidney stones.
Related category
• INORGANIC CHEMISTRY
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