Aluminium
post-transition metal · period 3 · group 13 · p-block
Aluminium (Aluminium in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel.
What the numbers say
At standard temperature and pressure Aluminium is a solid, sitting in period 3, group 13 of the p-block.
Its melting point of 933 K (660 °C) is the 66th highest of the 110 elements with a measured value — mid-range among the elements.
At 2.7 g/cm³ it is the 71st densest of 96 elements with a quoted density.
Pauling electronegativity is 1.61. Paired with oxygen (3.44) that is a difference of 1.83, which puts the bond predominantly ionic — expect a stable oxide ceramic.
In the solid state it takes a face-centered cubic structure — FCC packing gives 12 independent slip systems, which is why FCC metals are the ductile, formable ones.
It is reported in 3 oxidation states (1, 2, 3), which sets how many distinct compounds and phases it can form.
First identified in 1825.
Crystal structure
Solid Aluminium adopts a Face-centered Cubic arrangement, in the Cubic (isometric) system — axes a = b = c, angles α = β = γ = 90°. Symmetry controls the anisotropy of stiffness and thermal expansion, and the available slip systems set how far the metal deforms before it fractures.
Crystallographic examples
Aluminium or one of its compounds is a textbook example for these crystal systems:
- Cubic (isometric) — Cu, Al, Fe-α (BCC), NaCl, diamond, spinel MgAl₂O₄
- Trigonal (rhombohedral) — α-quartz, calcite CaCO₃, Bi, corundum Al₂O₃
Check it against computed structures
The structure search queries the Materials Project, OQMD and the Open Materials Database for computed crystal structures containing Al — with DFT formation energy, hull stability and band gap where the provider publishes them.
K 2 · L 8 · M 3
Properties
| Atomic number | 13 |
|---|---|
| Atomic mass | 26.98153857 u |
| Series | post-transition metal |
| Group | 13 |
| Period | 3 |
| Block | p-block |
| Phase at STP | Solid |
| Density | 2.7 g/cm³ |
| Melting point | 933.47 K (660 °C) |
| Boiling point | 2743 K (2470 °C) |
| Electronegativity (Pauling) | 1.61 |
| Electron configuration | [Ne] 3s² 3p¹ |
| Crystal structure | Face-centered Cubic |
| Oxidation states | 1,2,3 |
| Discovered | 1825 |
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See Al in context with all 118 elements.
Working with aluminium in a real design?
Ask the materials chat how Al behaves in your alloy system, what it does to weldability, and which grades to look at — with the source of every number named.