Aluminum (Al)
Element 13 · Post-transition metal · atomic mass 26.982 u · group 13, period 3
Electron shells: 2, 8, 3
Aluminum is the most abundant metal in the Earth's crust, yet it was once more precious than gold because it is so hard to separate from oxygen. Cheap electricity changed that in the 1880s.
Recycling aluminum takes about 5% of the energy needed to make it from ore.
- Atomic number
- 13
- Atomic mass
- 26.982 u
- Electron configuration
- [Ne] 3s² 3p¹
- Group · period · block
- 13 · 3 · p
- Oxidation states
- +3
- Electronegativity
- 1.61 (Pauling)
- Melting point
- 660 °C
- Boiling point
- 2,519 °C
- Density
- 2.7 g/cm³
- State at 20 °C
- Solid
- Appearance
- Silvery-white metal
- Also spelled
- Aluminium
- Discovered
- Hans Christian Ørsted, 1825
13 protons, and 13 electrons when neutral
IUPAC standard atomic weight
Boron group
Both spellings are accepted; this page uses the one in the source data
What Aluminum is used for
- Drink cans and foil
- Aircraft and vehicle bodies
- Power transmission lines
- Window frames and cladding
Atomic structure of Aluminum
A neutral aluminum atom has 13 protons and 13 electrons. Its most common isotope carries about 14 neutrons, which is where the mass number 27 comes from. Change the neutron count and you have a different isotope of aluminum; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 3. In orbital notation that is [Ne] 3s² 3p¹, leaving 3 valence electrons in the outer shell — the ones that do the chemistry.
3D electron orbitals
See where Aluminum's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Aluminum sits in the periodic table
Metals to the right of the d-block. Softer, lower-melting and more brittle than the transition metals, with more covalent character in their bonding.
Discovery and naming
Aluminum was discovered by Hans Christian Ørsted in 1825. Its name comes from Latin alumen, "alum".
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Aluminum?
The standard atomic weight of Aluminum is 26.982 u, as published by IUPAC's Commission on Isotopic Abundances and Atomic Weights.
How many protons, neutrons and electrons does Aluminum have?
Aluminum has 13 protons, because the atomic number is the proton count and that is what makes an atom Aluminum at all. A neutral Aluminum atom has the same number of electrons, 13. The neutron count varies by isotope; the most common one has about 14, since 27 − 13 = 14.
What is the electron configuration of Aluminum?
The electron configuration of Aluminum is [Ne] 3s² 3p¹. Its electrons are arranged 2, 8, 3 across 3 shells.
Is Aluminum a metal?
Yes. Aluminum is classified as a post-transition metal, on the metallic side of the table.
What group and period is Aluminum in?
Aluminum is in group 13 (the boron group), period 3, in the p-block. The group is its column and the period is its row.
What is the charge of Aluminum?
Aluminum most commonly forms a 3+ ion. It has 3 outer electrons available to lose.
What is the melting point of Aluminum?
Aluminum melts at 660 °C and boils at 2,519 °C. That puts it in the solids at everyday temperatures.
What is Aluminum used for?
Drink cans and foil, Aircraft and vehicle bodies, Power transmission lines, Window frames and cladding. Aluminum is the most abundant metal in the Earth's crust, yet it was once more precious than gold because it is so hard to separate from oxygen.
Who discovered Aluminum, and where does its name come from?
Aluminum (Al) was discovered by Hans Christian Ørsted in 1825. The name comes from Latin alumen, "alum".