Magnesium was first isolated in 1808 by Sir Humphry Davy, who evaporated the mercury from a magnesium amalgam made by electrolyzing a mixture of moist magnesia and mercuric oxide. It’s name comes from Magnesia, a district of Thessaly (Greece) where the mineral magnesia alba was first found.
It is a chemical element with the 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.
It is the eighth most abundant element in the Earth’s crust and the fourth most common element in the Earth making up 13% of the planet’s mass and a large fraction of the planet’s mantle. It is the third most abundant element dissolved in seawater, after sodium and chlorine.
It occurs naturally only in combination with other elements, where it invariably has a +2 oxidation state. The free element can be produced artificially, and is highly reactive (though in the atmosphere, it is soon coated in a thin layer of oxide that partly inhibits reactivity – see passivation). The free metal burns with a characteristic brilliant-white light. The metal is now obtained mainly by electrolysis of magnesium salts obtained from brine, and is used primarily as a component in aluminium-magnesium alloys, sometimes called magnalium or magnelium. Magnesium is less dense than aluminium, and the alloy is prized for its combination of lightness and strength.
Magnesium is the eleventh most abundant element by mass in the human body and is essential to all cells and some 300 enzymes. Magnesium ions interact with polyphosphate compounds such as ATP, DNA, and RNA. Hundreds of enzymes require magnesium ions to function. Magnesium compounds are used medicinally as common laxatives, antacids (e.g., milk of magnesia), and to stabilize abnormal nerve excitation or blood vessel spasm in such conditions as eclampsia.