Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic table) it occurs naturally only in combination with other elements and it almost always has an oxidation state of +2. It reacts readily with air to form a thin passivation coating of magnesium oxide that inhibits further corrosion of the metal. The free metal burns with a brilliant-white light. The metal is obtained mainly by electrolysis of magnesium salts obtained from brine. It is less dense than aluminium and is used primarily as a component in strong and lightweight alloys that contain aluminium.

In the cosmos, magnesium is produced in large, aging stars by the sequential addition of three helium nuclei to a carbon nucleus. When such stars explode as supernovas, much of the magnesium is expelled into the interstellar medium where it may recycle into new star systems. Magnesium 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. This element is the eleventh most abundant element by mass in the human body and is essential to all cells and some 300 enzymes. Magnesium ions interact with polyphosphate compounds such as ATP, DNA, and RNA. Hundreds of enzymes require magnesium ions to function. Magnesium compounds are used medicinally as common laxatives and antacids (such as milk of magnesia), and to stabilize abnormal nerve excitation or blood vessel spasm in such conditions as eclampsia.

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Atomic properties

Standard atomic weight24.305 ±0.002 [24.304 … 24.307]
Atomic mass24.3052 u

Atomic radii

Radius (empirical)150 pm
Radius (calculated)145 pm
Covalent radius141 ±7 pm
Van der Waals radius173 pm

Atomic shell

Electron configurationNe 3s2
Ionization energy(1st) 7.646236 eV
(2nd) 15.035271 eV
(3rd) 80.1436 eV
(4th) 109.2654 eV
(5th) 141.33 eV
Shell model

Physical properties

Density1.738 g·cm−3 (293.1 K)
Molar volume1.4·10-5 m3·mol−1
Speed of sound4,602 m·s−1 (293.1 K)


Melting point923 K
Boiling point1,363 K
Liquid range440 K


Melting enthalpy8.7 kJ·mol-1
Enthalpy of vaporization128 kJ·mol-1
Binding energy146 kJ·mol-1

Heat and conductivity

Specific heat capacity1,023 J·kg−1·K−1
Thermal conductivity160 W·m-1·K-1
Expansion coefficient8.2·10-6 K-1
Work function3.66 eV


Mohs hardness2.5
Brinell hardness260 NM·m-2

Elastic properties

Young’s modulus45 GPa
Shear modulus17 GPa
Bulk modulus45 GPa
Poisson’s ratio0.29

Electrical properties

Electrical conductivity2.27·107 S·m-1
Resistance4.399·10-8 Ωm


Magnetic susceptibility1.31·10-5 cm3·mol−1 (298 K)

Optical properties

Reflectivity74 %

Chemical properties

Basicitymoderately basic
Oxidation state1, 2
Standard potential-2.372 V (Mg2+ + 2e- → Mg)


Pauling scale1.31
Sanderson scale1.32
Allred-Rochow scale1.23
Mulliken scale1.37
Allen scale1.293
Ghosh-Gupta scale3.61 eV
Boyd-Edgecombe scale1.32
Nagle scale1.32
Pearson absolute negativity3.75 eV

Other properties

Natural occurrenceprimordial
Crystal structureHexagonal close-packed
Goldschmidt Classificationlithophile
Superconductorwithout transition tempperature
Price/kg2.32 USD

Natural abundances

600,000 ppb ≈ 6.03·1015 M☉
700,000 ppb ≈ 1.39·1015 Mt
1.2·108 ppb ≈ 120 kg
Earth’s crust
2.9·107 ppb ≈ 8.03·108 Mt
1.326·106 ppb ≈ 1,810 Mt
Flowing water
4,100 ppb ≈ 65.6 Gt
Human body
270,000 ppb ≈ 18.9 g