Question

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

Answer 1

`"Al"^(3+): 1s^2 2s^2 2p^6`

Explanation:

Your starting point here will be the electron configuration of a neutral aluminium atom, `"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

`"Al: " 1s^2 2s^2 2p^6 3s^2 3p^1`

Now, when aluminium forms `3+` cations, `"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 `-> "1 e"^(-)`
• the 3s orbital `-> "2 e"^(-)`

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

`color(green)(|bar(ul(color(white)(a/a)color(black)("Al"^(3+): 1s^2 2s^2 2p^6)color(white)(a/a)|)))`