Question

What is the number of valence electrons in aluminum?

Answer 1

The electron configuration for Aluminum is

$1s^{2}2s^{2}2P663s^{2}3P^1$

The first 10 electrons are in the filled first and second shells.

This leaves only three electrons in the third shell $3s^{2}3p^1$

$13-10=3$

so there are only 3 valance electrons