# What is the electron configuration for "Al"^(3+)?

Aug 4, 2016

${\text{Al}}^{3 +} : 1 {s}^{2} 2 {s}^{2} 2 {p}^{6}$

#### Explanation:

Your starting point here will be the electron configuration of a neutral aluminium atom, $\text{Al}$.

Aluminium is located in period 3, group 13, and has an atomic number equal to $13$. This tells you that the electron configuration of a neutral aluminium atom must account for a total of $13$ electrons.

The electron configuration of the neutral atom looks like this

$\text{Al: } 1 {s}^{2} 2 {s}^{2} 2 {p}^{6} 3 {s}^{2} 3 {p}^{1}$

Now, when aluminium forms $3 +$ cations, ${\text{Al}}^{3 +}$, it loses $3$ electrons from its outermost energy shell.

In this case, the $3$ electrons will come from the third energy shell. To be precise, these electrons will come from

• one 3p orbital $\to {\text{1 e}}^{-}$
• the 3s orbital $\to {\text{2 e}}^{-}$

This means that the electron configuration of the aluminium cation looks like this

$\textcolor{g r e e n}{| \overline{\underline{\textcolor{w h i t e}{\frac{a}{a}} \textcolor{b l a c k}{{\text{Al}}^{3 +} : 1 {s}^{2} 2 {s}^{2} 2 {p}^{6}} \textcolor{w h i t e}{\frac{a}{a}} |}}}$