Element 13 · Post-transition metal
Aluminium (Al) — Element 13
Latin alumen — alum
Aluminium (Al) is a post-transition metal in Period 3, Group 13 of the periodic table with atomic number 13, standard atomic weight 26.982 u, and ground-state electron configuration [Ne] 3s² 3p¹. At standard temperature and pressure it is classified as a solid with 3 valence electrons and common oxidation states +3.
Aircraft, packaging, power lines
What are the atomic properties and physical constants of Aluminium?
Reference constants compiled from IUPAC standard atomic weights, the NIST Atomic Spectra Database, and the CRC Handbook.
- Atomic number (Z)
- 13
- Standard atomic mass
- 26.982 u
- Chemical family
- Post-transition metal
- Ground-state configuration
- [Ne] 3s² 3p¹
- Electrons per shell
- 2, 8, 3
- Valence electrons
- 3
- Common ion charges / oxidation states
- +3
- Phase at STP
- Solid
- Pauling electronegativity
- 1.61 Pauling
- First ionization energy
- 577 kJ/mol
- Atomic radius
- 118 pm
- Melting point
- 660 °C
- Boiling point
- 2,470 °C
- Discovery year
- 1825
- Table coordinate
- Period 3, Group 13
- Radioactivity
- Has stable isotope(s)
How are electrons arranged across Aluminium’s shells?
A neutral Aluminium atom contains 13 electrons distributed across 3 occupied principal energy shells ([Ne] 3s² 3p¹). The table below compares Aluminium’s shell occupancy against each shell’s theoretical 2n² capacity.
| Principal Shell (n) | Spectroscopic Letter | Electrons in Al | Max Shell Capacity (2n²) |
|---|---|---|---|
| n = 1 | K | 2 e⁻ | 2 e⁻ |
| n = 2 | L | 8 e⁻ | 8 e⁻ |
| n = 3 | M | 3 e⁻ | 18 e⁻ |
Frequently Asked Questions about Aluminium (Al)
What is the atomic mass and atomic number of Aluminium (Al)?
Aluminium (Al) has atomic number Z = 13 (13 protons in its nucleus) and an IUPAC standard atomic weight of 26.982 u. It sits in Period 3, Group 13 and is classified as a post-transition metal.
What is the ground-state electron configuration of Aluminium?
The neutral ground-state electron configuration of Aluminium (Z = 13) is [Ne] 3s² 3p¹. Across its 3 occupied principal shells (n = 1 to n = 3), the electrons per shell are 2, 8, 3, with 3 valence electrons participating in bonding.
What are the common ion charges and electronegativity of Aluminium?
Aluminium commonly forms +3 oxidation states or ion charges in compounds. Its Pauling electronegativity is 1.61 and its first ionization energy is 577 kJ/mol.
When was Aluminium discovered and what is it used for?
Aluminium was discovered in 1825 (Latin alumen — alum). Aircraft, packaging, power lines
How does Aluminium compare to neighboring elements?
Other post-transition metal elements: