Question

how many valence electrons in Al3+

Answer 1

The original electron configuration for an aluminum atom is

1 s2 2 s2 2 p6 3 s2 3 p1

The electrons in the third (valence) shell of the atom are contained in the

3 s2 3 p1

sublevels. When these electrons are gone, so is the third shell of the aluminum atom, and what remains is

1 s2 2 s2 2 p6

with a 3+ charge. So Al has 10 valance electrons