How many electrons are in Al3+?

There are 10 electrons in the ion of Al+3. We can easily determine this by knowing that a neutral atom of Al has 13 protons and 13 electrons. So to get the + 3 charge we need a remaining of 3 protons to give us that charge, since the number of protons can't change we can reduce the number of electrons so we can get that electrical charge of + 3.

atomic number of aluminium = 13

so the number of electrons=13

aluminium cation, has 3 positive charge which it attains after losing 3 electrons (protons are not lost, there remain in the nucleus of the atom

electrons in Al3 + = 13 - 3 = 10