Question: how many electrons are in the outermost shell of the aluminum cation al3+?
Answer: 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. Now, when aluminium forms 3+ cations, Al3+ , it loses 3 electrons from its outermost energy shell.