Aluminium (Al)

Post-transition metals · Period 3 · Solid

Explore aluminium isotopes Locate in periodic table

Element identity

Atomic number (Z): 13
Symbol: Al
Atomic weight / isotope mass number: 26.981 5384(3)
Category: Post-transition metals
Physical state (reference): Solid
Period: 3
Group (reference): 13
Block: p

Physical properties

Appearance: Silvery gray metallic
Density: 2.70 g·cm⁻³
Melting point: 933.47 K / 660.32 °C / 1220.58 °F
Boiling point: 2743 K / 2470 °C / 4478 °F
Sublimation point: Not available

Atomic and material properties

Electron configuration: [Ne] 3s² 3p¹
Electrons per shell: K2 L8 M3
Oxidation states: 3, 2, 1, −1, −2
Electronegativity (Pauling): 1.61
Atomic radius: 118 pm
Covalent radius: 121±4 pm
Molar ionization energies: 1st: 577.5 kJ·mol⁻¹ 2nd: 1816.7 kJ·mol⁻¹ 3rd: 2744.8 kJ·mol⁻¹ 4th: 11,577 kJ·mol⁻¹ 5th: 14,842 kJ·mol⁻¹ 6th: 18,379 kJ·mol⁻¹ 7th: 23,326 kJ·mol⁻¹ 8th: 27,465 kJ·mol⁻¹ 9th: 31,853 kJ·mol⁻¹ 10th: 38,473 kJ·mol⁻¹ 11th: 42,647 kJ·mol⁻¹ 12th: 201,266 kJ·mol⁻¹ 13th: 222,316 kJ·mol⁻¹
Thermal conductivity: 237 W·m⁻¹·K⁻¹
Molar heat capacity: 24.20 J·mol⁻¹·K⁻¹
Crystal structure: Face-centered cubic
CAS number: 7429-90-5

Property source: Wikipedia — Aluminium, adapted from the Nuclides App snapshot. Quoted conditions and qualifiers are retained.

Sources and interpretation

Snapshot exported 24 October 2026 from the element assets used by Nuclides. Properties are a reference compilation, not a new evaluation. Missing values are shown as “Not available”. Density and phase depend on temperature, pressure and allotrope; retained conditions are part of the quoted property.

Atomic weight is dimensionless. Parentheses give uncertainty in the last quoted digits. A single integer in square brackets is an isotope mass number, not a standard atomic weight. The snapshot can differ from current evaluations; consult CIAAW standard atomic weights and the IUPAC periodic table for current values and conventions.

Element properties in the App snapshot are adapted from Wikipedia. Each element page links to its source article; text adaptations are available under CC BY-SA 4.0. No third-party images are included.

Go from elements to nuclear data

Keep Nuclides on your phone.

Explore connected element and nuclide references, decay chains and calculators in the app. See each store for pricing and in-app purchases.