Aluminium (Al): Bohr Model, Protons, Neutrons & Electrons
Aluminium is element number 13, a post-transition metal in group 13, period 3. Its atom has 13 protons, 14 neutrons and 13 electrons arranged in 3 shells: 2, 8, 3.
Protons, neutrons and electrons in aluminium
The atomic number of aluminium is 13, so every aluminium atom has 13 protons. A neutral atom has the same number of electrons, 13. The number of neutrons depends on the isotope: neutrons = mass number − atomic number. For aluminium-27, that is 27 − 13 = 14 neutrons.
How to draw the Bohr model of aluminium
- Draw the nucleus and write 13 p⁺ and 14 n⁰ inside it.
- Draw the first shell and put 2 electrons on it (the first shell holds at most 2).
- Draw the second shell and put 8 electrons on it.
- Draw the third shell and put 3 electrons on it.
- Check: 2 + 8 + 3 = 13 electrons, the same as the number of protons.
Electron configuration
The electron configuration of aluminium is [Ne] 3s² 3p¹. Its 3 outer electrons decide how it reacts: it tends to lose them, forming Al³⁺ ions.
Key facts about aluminium
| Symbol | Al |
|---|---|
| Atomic number | 13 |
| Relative atomic mass | 26.982 |
| Group · period · block | group 13 · period 3 · p-block |
| Type | Post-transition Metal |
| State at 25 °C | solid |
| Electron shells | 2, 8, 3 |
| Electron configuration | [Ne] 3s² 3p¹ |
| Valence electrons | 3 |
| Common ion | Al³⁺ |
| Electronegativity (Pauling) | 1.61 |
| First ionisation energy | 5.99 eV (578 kJ/mol) |
| Atomic radius (empirical) | 125 pm |
Where aluminium sits on the periodic table
Frequently asked questions
How many protons, neutrons and electrons does aluminium have?
Aluminium has 13 protons and 13 electrons (atomic number 13). Its most common isotope, aluminium-27, has 27 − 13 = 14 neutrons.
What is the electron configuration of aluminium?
[Ne] 3s² 3p¹. In shells that is 2, 8, 3.
How many valence electrons does aluminium have?
3. Aluminium is in group 13, and its outer shell holds 3 electrons.
Where is aluminium on the periodic table?
In group 13, period 3, in the p-block. It is a post-transition metal.
