Magnesium

Two electrons in a 3s orbital beyond a neon core give magnesium its defining character: it surrenders both without hesitation, making Mg2+ the only oxidation state that matters in practice. Sitting at period 3, group 2 — directly below beryllium and above calcium — it is the quintessential alkaline earth metal, reactive enough to reduce water slowly at room temperature yet stable enough to serve as a structural material. Its low electronegativity of 1.31 means it cedes electron density to almost every nonmetal it encounters, and its relatively large atomic radius of 145 pm compared to beryllium means weaker nuclear hold on those outer electrons. That combination of low density, high reactivity, and predictable +2 chemistry places magnesium at intersections ranging from biochemistry to aerospace.

Automotive and aerospace engineers prize magnesium alloys for their exceptional strength-to-weight ratio — roughly one-third lighter than aluminum and four times lighter than steel, alloys such as AZ31 and AZ91 appear in car seats, steering columns, laptop casings, and helicopter gearboxes. In pyrotechnics, magnesium powder burns at around 3,100 degrees Celsius, producing intense white light, which is why it has been used in military flares, incendiary munitions, and camera flash powder since the 19th century. Magnesium oxide (MgO) is a refractory lining material in furnaces because of its melting point near 2,852 degrees Celsius. In agriculture, magnesium sulfate — sold as Epsom salt — corrects magnesium deficiency in soils and is used as a foliar spray on crops. Steel production also consumes magnesium metal to desulfurize pig iron before casting.

Scottish chemist Joseph Black recognized in 1755 that magnesia alba (magnesium carbonate) was chemically distinct from lime (calcium oxide), identifying it as the product of a previously unrecognized earth. The element itself remained unextracted for another half century. Humphry Davy performed electrolysis experiments in 1808 that yielded small amounts of an amalgam he believed contained a new metal, which he named magnium; that name never caught on and magnesium — derived from Magnesia, a district in Thessaly, Greece, where magnesium minerals were mined — took its place. The first substantial quantity of pure magnesium was isolated by French chemist Antoine-Alexandre Brutus Bussy in 1831, who reduced magnesium chloride with potassium metal. Commercial production became viable after Robert Bunsen developed an electrolytic process in 1852. During World War II, magnesium production scaled dramatically because the metal was critical for incendiary bombs and aircraft frames, making it briefly one of the most strategically important metals in the world.

Magnesium ranks eighth among elements by mass in Earth's crust at roughly 2.1 percent, and it is the third most abundant element dissolved in seawater after chlorine and sodium, present at about 1,290 milligrams per liter. Most terrestrial magnesium is locked in silicate minerals — olivine ((Mg,Fe)2SiO4) dominates the upper mantle and is one of the most abundant minerals in the planet's interior, while dolomite (CaMg(CO3)2) and magnesite (MgCO3) form thick sedimentary sequences on every continent. In biological systems, magnesium cycles through the food chain because chlorophyll — the light-harvesting pigment in every plant and alga — carries a magnesium ion at the center of its porphyrin ring, making photosynthesis on Earth fundamentally dependent on the element. Cosmically, magnesium is one of the more abundant elements, formed in massive stars through carbon and neon burning.

Magnesium chloride (MgCl2) is extracted directly from seawater and used in road de-icing, dust suppression, and as a coagulant in tofu production. Magnesium oxide (MgO), known as magnesia, serves as both a refractory material in high-temperature furnaces and an antacid and laxative in medicine. Magnesium hydroxide (Mg(OH)2), sold as milk of magnesia, neutralizes stomach acid and acts as a gentle laxative. Magnesium sulfate (MgSO4·7H2O) — Epsom salt — has agricultural, therapeutic, and industrial uses ranging from bath salts to anesthetic adjuncts in surgery. Grignard reagents, organomagnesium halides of the general form RMgX, are among the most versatile carbon–carbon bond-forming tools in organic synthesis, discovered by Victor Grignard in 1900. Chlorophyll a (C55H72MgN4O5) coordinates magnesium at its core and drives the light reactions of photosynthesis across nearly all plant life.

• Magnesium is the fourth most abundant mineral in the human body, and every known enzyme that transfers phosphate groups — including those driving ATP synthesis — requires a magnesium ion as a cofactor, meaning your cells cannot generate usable energy without it.
• Burning magnesium cannot be extinguished with water or carbon dioxide; it is hot enough to split water molecules and reduce CO2 to carbon, which is why magnesium fires require dry sand or Class D extinguishers.
• The word 'magnesium' and the word 'manganese' both derive from the same Greek place name, Magnesia, because early chemists confused the two minerals found in that region — a source of genuine historical muddle that persisted for decades.
• Despite being highly reactive, magnesium resists corrosion in dry air because it forms a thin, tightly adhering oxide layer that passivates the surface — the same principle that protects aluminum, though magnesium's protection breaks down in saltwater far more readily.
• A single magnesium atom sits at the center of each chlorophyll molecule, and because land plants and phytoplankton together fix roughly 120 billion tonnes of carbon per year, magnesium is indirectly responsible for most of the oxygen in Earth's atmosphere.