Magnesium
alkaline earth metal · period 3 · group 2 (alkaline earth metals) · s-block
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray solid which bears a close physical resemblance to the other five elements in the second column (group 2, or alkaline earth metals) of the periodic table: all group 2 elements have the same electron configuration in the outer electron shell and a similar crystal structure. This element is produced in large, aging stars from the sequential addition of three helium nuclei to a carbon nucleus.
What the numbers say
At standard temperature and pressure Magnesium is a solid, sitting in period 3, group 2 of the s-block.
Its melting point of 923 K (650 °C) is the 67th highest of the 110 elements with a measured value — mid-range among the elements.
At 1.738 g/cm³ it is the 80th densest of 96 elements with a quoted density.
Pauling electronegativity is 1.31. Paired with oxygen (3.44) that is a difference of 2.13, which puts the bond predominantly ionic — expect a stable oxide ceramic.
In the solid state it takes a simple hexagonal structure — hexagonal packing offers few easy slip systems, so properties are anisotropic and formability is limited.
It is reported in 2 oxidation states (1, 2), which sets how many distinct compounds and phases it can form.
First identified in 1755.
Crystal structure
Solid Magnesium adopts a Simple Hexagonal arrangement, in the Hexagonal system — axes a = b ≠ c, angles α = β = 90°, γ = 120°. Symmetry controls the anisotropy of stiffness and thermal expansion, and the available slip systems set how far the metal deforms before it fractures.
Where magnesium shows up in engineering materials
1 entry in the materials library names it directly:
- Magnesium AZ31B — Mg-Al-Zn
Crystallographic examples
Magnesium or one of its compounds is a textbook example for these crystal systems:
- Cubic (isometric) — Cu, Al, Fe-α (BCC), NaCl, diamond, spinel MgAl₂O₄
- Hexagonal — Mg, Zn, Ti-α, graphite, ZnO (wurtzite), ice Ih
Check it against computed structures
The structure search queries the Materials Project, OQMD and the Open Materials Database for computed crystal structures containing Mg — with DFT formation energy, hull stability and band gap where the provider publishes them.
K 2 · L 8 · M 2
Properties
| Atomic number | 12 |
|---|---|
| Atomic mass | 24.305 u |
| Series | alkaline earth metal |
| Group | 2 |
| Period | 3 |
| Block | s-block |
| Phase at STP | Solid |
| Density | 1.738 g/cm³ |
| Melting point | 923 K (650 °C) |
| Boiling point | 1363 K (1090 °C) |
| Electronegativity (Pauling) | 1.31 |
| Electron configuration | [Ne] 3s² |
| Crystal structure | Simple Hexagonal |
| Oxidation states | 1,2 |
| Discovered | 1755 |
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See Mg in context with all 118 elements.
Working with magnesium in a real design?
Ask the materials chat how Mg behaves in your alloy system, what it does to weldability, and which grades to look at — with the source of every number named.