magnesium

Lightweight, very ductile and malleable, silver-white, metallic element, atomic number 12, relative atomic mass 24.305. It is one of the alkaline-earth metals, and the lightest of the commonly used metals. Magnesium silicate, carbonate, and chloride are widely distributed in nature. The metal is used in alloys, flares, and flash bulbs. It is a necessary trace element in the human diet, and green plants cannot grow without it since it is an essential constituent of the photosynthetic pigment chlorophyll (C₅₅H₇₂MgN₄O₅).

It was named after the ancient Greek city of Magnesia, near where it was first found. It was first recognized as an element by Scottish chemist Joseph Black in 1755 and discovered in its oxide by English chemist Humphry Davy 1808. Pure magnesium was isolated in 1828 by French chemist Antoine-Alexandre-Brutus Bussy.