Overview

Magnesium is a chemical element represented by the symbol Mg and the atomic number 12. It most commonly forms a divalent cation (Mg2+) and is a member of the group of alkaline earth metals. Magnesium is widespread in the Earth's crust and in the oceans; it is one of the more abundant elements both in the Earth's crust and in the known universe.

Physical and chemical properties

As a metal, magnesium is relatively light and has a silvery metallic appearance when freshly exposed. The free metal oxidizes readily in air; an outer oxide layer forms that slows further corrosion. Magnesium metal has characteristic chemical behavior: it commonly attains the +2 oxidation state and its ions are strongly hydrated and soluble in water. When burned in air, finely divided magnesium gives an intense white flame, a property exploited in illumination and some pyrotechnic applications. The element reacts with a range of nonmetals and oxidizing agents; see notes on chemical reactivity.

Isotopes

Magnesium occurs naturally as a mixture of stable isotopes. These isotopes are used in research on geochemical processes, in isotope geochemistry to trace origins of rocks and minerals, and in studies of planetary formation. Radioactive isotopes of magnesium are produced in laboratories for specialized scientific and medical research.

Occurrence and production

Magnesium is present in a variety of minerals, including magnesite and dolomite, and is abundant in seawater as dissolved ions. In stars and stellar explosions, magnesium is produced by nuclear fusion processes: successive addition of helium nuclei (alpha capture) to lighter elements such as carbon and other intermediates during advanced burning stages and in supernovae. On Earth, commercial production of metallic magnesium is commonly achieved by electrolytic or thermal reduction methods applied to salts derived from brines and minerals.

Biological role

Magnesium ions are essential to all known living cells. In humans and many organisms magnesium is among the more abundant elements in the human body by mass and is required for normal physiological function. It stabilizes and interacts with phosphorylated biomolecules such as ATP, and influences the structure and reactivity of nucleic acids like DNA and RNA. Hundreds of enzymes use magnesium as a cofactor, affecting metabolism, nucleic acid processing and other cellular processes. In plants the central atom of chlorophyll is magnesium, making the element directly important for photosynthesis and primary productivity; this underlies the inclusion of magnesium-containing compounds in some fertilizers.

Applications

Magnesium's combination of low density and useful mechanical properties makes it valuable in lightweight structural alloys used in aerospace, automotive and electronic applications. It is commonly alloyed with aluminum and other elements to achieve desired strength and corrosion resistance. Powdered magnesium or thin strips are used in flares, fireworks and photographic flash devices because of the bright white combustion. Magnesium compounds have diverse uses in agriculture, chemical manufacturing, and as precursors for other materials.

History and naming

The element's name derives from minerals associated with the ancient region of Magnesia. Metallic magnesium was first isolated in the early 19th century by electrochemical methods developed by several chemists of that era. Over time, improved extraction and refining processes have made magnesium widely available for industrial use.

Safety and handling

Metallic magnesium in bulk is relatively safe under normal conditions, but fine magnesium powder and thin ribbons are flammable and can ignite easily, producing extremely hot burns that are difficult to extinguish. Reactions with strong oxidizers and some acids can be vigorous. In laboratory and industrial settings appropriate precautions, including control of dust and ignition sources, must be observed to limit fire and explosion risks.

Further reading and resources