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12Mg24.31

Element 12, an alkaline earth metal

Magnesium

A light metal that burns with a dazzling white light, and the atom at the center of every chlorophyll molecule.

At a glance

Symbol
Mg
Atomic number
12
Average atomic mass
24.31
Group
2
Period
3
Family
alkaline earth metal
Electron configuration
1s² 2s² 2p⁶ 3s², or [Ne] 3s²
Valence electrons
2
Electronegativity
1.31
Common ions
Mg²⁺

On the table

Periodic table with Magnesium highlighted123456789101112131415161718123456757-7189-103HHeLiBeBCNOFNeNaMgAlSiPSClArKCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKrRbSrYZrNbMoTcRuRhPdAgCdInSnSbTeIXeCsBaLaCePrNdPmSmEuGdTbDyHoErTmYbLuHfTaWReOsIrPtAuHgTlPbBiPoAtRnFrRaAcThPaUNpPuAmCmBkCfEsFmMdNoLrRfDbSgBhHsMtDsRgCnNhFlMcLvTsOg

Period 3, group 2. The other alkaline earth metals are tinted, and every cell opens its own article.

Electrons and bonding

Mg

Two valence electrons, which magnesium gives up to form the Mg²⁺ ion in its compounds.

Properties

State at 25 °C
solid
What it looks like
light, silvery-white metal
Melting point
650 °C
Boiling point
1090 °C
Density
1.74 g/cm³
Flame test
no color of its own; the metal burns with a brilliant white light

Where it is found

About 2% of the crust, in minerals such as dolomite, magnesite and olivine. Seawater holds about 1.3 grams per liter, and for decades much of the world's magnesium was extracted from the sea. Today China produces most of it.

Discovery and name

Joseph Black recognized magnesia as different from lime in 1755, and Humphry Davy isolated an impure sample of the metal in 1808. The name comes from Magnesia, a district in Greece where magnesium minerals were found.

What it is used for

Light alloys for car parts, laptop and camera bodies, bicycles and aircraft, since magnesium is about a third lighter than aluminum. It also goes into aluminum drink cans, flares and fireworks, and the production of iron and titanium. Epsom salt soothes sore muscles and milk of magnesia settles stomachs.

In compounds

MgOmagnesium oxideMg(OH)₂magnesium hydroxide, milk of magnesiaMgSO₄·7H₂OEpsom saltMgCO₃magnesiteMgCl₂magnesium chloride, a de-icerC₅₅H₇₂MgN₄O₅chlorophyll a

Handle with care

Burning magnesium is so hot that water makes the fire worse by releasing hydrogen, and the light can hurt your eyes. Fine powder and shavings catch fire easily.