In Nature:
Magnesium is a chemical element with symbol Mg and atomic number 12. It is a shiny gray solid which bears a close physical resemblance to the other five elements in the second column (Group 2, or alkaline earth metals) of the periodic table: all Group 2 elements have the same electron configuration in the outer electron shell and a similar crystal structure.
Elemental magnesium is a gray-white lightweight metal, two-thirds the density of aluminium. It tarnishes slightly when exposed to air, although, unlike the other alkaline earth metals, an oxygen-free environment is unnecessary for storage because magnesium is protected by a thin layer of oxide that is fairly impermeable and difficult to remove. Magnesium has the lowest melting (923 K (1,202 °F)) and the lowest boiling point 1,363 K (1,994 °F) of all the alkaline earth metals.
Magnesium is probably one of the most common metals distributed in nature, constituting about 2.4% of the earth’s crust. The metal, however, does not occur in nature in elemental form. The principal minerals are dolomite [CaMg(CO3)2], magnesite MgCO3; carnallite KCl•MgCl2•6H2O, and silicate materials, such as talc Mg3(Si4O10)(OH)2 and asbestos H4Mg3Si2O9. Magnesium also is found in seawater, natural underground brines and salt deposits. Its concentration in sea water is 1,350 mg/L. Magnesium also occurs in all plants. Its porphyrin complex, chlorophyll, is essential for photosynthesis.
In Human body:
It is an essential nutrient element for humans. The dietary requirement for adults is about 300 mg per day. Magnesium plays an important role in over 300 enzymatic reactions within the body including the metabolism of food, synthesis of fatty acids and proteins, and the transmission of nerve impulses. It is one of the seven essential macrominerals; these are minerals that need to be consumed in relatively large amounts-at least 100 milligrams per day.
