Magnesium,  ₁₂Mg

General properties
Pronunciation	/mæɡˈniːziəm/ ​(mag-NEE-zee-əm)
Appearance	shiny grey solid
Standard atomic weight (Ar, standard)	[24.304, 24.307]
Magnesium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Be ↑ Mg ↓ Ca sodium ← magnesium → aluminium
Atomic number (Z)	12
Group	group 2 (alkaline earth metals)
Period	period 3
Block	s-block
Element category	alkaline earth metal
Electron configuration	[Ne] 3s2
Electrons per shell	2, 8, 2
Physical properties
Phase at STP	Mg: Solid
Melting point	923 K ​(650 °C, ​1202 °F)
Boiling point	1363 K ​(1091 °C, ​1994 °F)
Density (near r.t.)	1.738 g/cm3
when liquid (at m.p.)	1.584 g/cm3
Heat of fusion	8.48 kJ/mol
Heat of vaporization	128 kJ/mol
Molar heat capacity	24.869 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 701 773 861 971 1132 1361
Atomic properties
Oxidation states	+1,+2 (a strongly basic oxide)
Electronegativity	Pauling scale: 1.31
Ionization energies	1st: 737.7 kJ/mol 2nd: 1450.7 kJ/mol 3rd: 7732.7 kJ/mol (more)
Atomic radius	empirical: 160 pm
Covalent radius	141±7 pm
Van der Waals radius	173 pm
Spectral lines of magnesium
Other properties
Natural occurrence	Mg: Primordial
Crystal structure	​hexagonal close-packed (hcp)
Speed of sound thin rod	4940 m/s (at r.t.) (annealed)
Thermal expansion	24.8 µm/(m·K) (at 25 °C)
Thermal conductivity	156 W/(m·K)
Electrical resistivity	43.9 nΩ·m (at 20 °C)
Magnetic ordering	paramagnetic
Magnetic susceptibility	+13.1·10−6 cm3/mol (298 K)
Young's modulus	45 GPa
Shear modulus	17 GPa
Bulk modulus	35.4 GPa
Poisson ratio	0.290
Mohs hardness	1–2.5
Brinell hardness	44–260 MPa
CAS Number	7439-95-4
History
Naming	after Magnesia, Greece
Discovery	Joseph Black (1755)
First isolation	Humphry Davy (1808)
Main isotopes of magnesium
Iso­tope Abun­dance Half-life (1/2) Decay mode Pro­duct 24Mg 79.0% stable 25Mg 10.0% stable 26Mg 11.0% stable
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Magnesium

Magnesium ( /mæɡˈniːziəm/ mag-NEE-zee-əm) is a chemical element with the symbol Mg, atomic number 12 and common oxidation state +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust, where it constitutes about 2% by mass, and ninth in the known universe as a whole. This preponderance of magnesium is related to the fact that it is easily built up in supernova stars from a sequential addition of three helium nuclei to carbon (which in turn is made from three helium nuclei). Magnesium ion's high solubility in water helps ensure that it is the third most abundant element dissolved in seawater.