How many valence electrons are in Al^3+?

3 valence electrons

Explanation:

Al⁺³ has the electron configuration a of 1s² 2s² 2p⁶ 3s² and 3p¹. Since we are looking for the valence electrons, we are looking for the outer most electrons. These would be in the 3s² and 3p¹ sublevels. Adding the superscripts of these sub levels, we get:

2 + 1 = 3

∴ there are 3 valence electrons in Al⁺³

We can also check this by taking a quick look at the periodic table. We can find aluminum on the right hand side underneath boron in group 3A. There is something really cool about all the A groups. Notice the number before the A groups? 1A, 2A, 3A ... 8A. Well, it goes all the way up to 8A. There are exactly 8 valence electrons in an octet a. k. a. "the happy state of elements." In each group, it can be seen that it has a certain number of electrons by its group number. Your alkali have 1 valence electrons ... all the way to your noble gases which have 8 valence electrons. Seeing that aluminum is in group 3A, we can, thus determine that it has 3 valence electrons.