<unk>  is a chemical element with the symbol<unk>  and atomic number 12. It is a shiny gray solid which shares many physical and chemical properties with the other five alkaline earth metals (group 2 of the periodic table). This element is produced in large, aging stars from the sequential addition of three helium nuclei to a carbon nucleus. When such stars explode as supernovas, much of the<unk>  is expelled into the interstellar medium where it may recycle into new star systems.<unk>  is the eighth most abundant element in the Earth's crust and the fourth most common element in the Earth (after iron, oxygen and silicon), 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.<unk>  occurs naturally only in combination with other elements, where it almost always has a +2 oxidation state. The free element (metal) 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<unk>  salts obtained from brine, and is used primarily as a component in aluminium-magnesium alloys, sometimes called<unk> nalium or<unk> .<unk>  is less dense than aluminium, and the alloy of the two is prized for its combination of lightness and strength. This element is the eleventh most abundant element by mass in the human body and is essential to all cells and some 300 enzymes.<unk>  ions interact with polyphosphate compounds such as ATP, DNA, and RNA. Hundreds of enzymes require<unk>  ions to function.<unk>  compounds are used medicinally as common laxatives, antacids (e.g., milk of<unk> nesia), and to stabilize abnormal nerve excitation or blood vessel spasm in such conditions as eclampsia.
Magnesium
Calcium
Potassium
Calamine
Milium 
Calcium carbonate
Copper 
Folate