Aluminum (Al)
Aluminum is element 13, a post-transition metal in period 3, group 13 of the periodic table. At room temperature it is a solid.
Electron configuration [Ne] 3s2 3p1
Electrons per shell 2, 8, 3
Aluminum data
| Atomic number | 13 |
|---|---|
| Symbol | Al |
| Atomic mass | 26.982 u |
| Category | Post-transition metal |
| Group | 13 |
| Period | 3 |
| Block | p |
| State at 25 °C | solid |
| Melting point | 933 K (659.9 °C) |
| Boiling point | 2792 K (2518.9 °C) |
| Density | 2.7 g/cm³ |
| Electronegativity (Pauling) | 1.61 |
| Atomic radius | 118 pm |
| 1st ionization energy | 578 kJ/mol |
| Electron affinity | -43 kJ/mol |
| Oxidation states | +1, +3 |
| Common ion charge | 3+ |
| Discovered | Known since antiquity |
Orbital diagram
Each box is one orbital holding up to two electrons of opposite spin. Following Hund’s rule, electrons spread out singly across a subshell before pairing.
Work through aluminum’s configuration and its ions →
Where aluminum sits
Aluminum belongs to the post-transition metals. Its Pauling electronegativity of 1.61 is mid-range; see the electronegativity chart and periodic trends for context. To use its mass in a calculation, try the molar mass calculator.
Aluminum FAQ
What is the electron configuration of aluminum?
Aluminum (Z = 13) has the configuration 1s2 2s2 2p6 3s2 3p1. In noble-gas shorthand that is [Ne] 3s2 3p1.
How many valence electrons does aluminum have?
3 (outer shell (n = 3)).
What is the atomic mass of aluminum?
The standard atomic weight of aluminum is 26.982 u, so one mole weighs 26.982 g.
Is aluminum a metal?
Yes. Aluminum is a post-transition metal.
What is the charge of a aluminum ion?
Aluminum most commonly forms Al3+.