Multiple choice general knowledge science & technology How many electrons are found in the outermost shell of aluminium (al atomic number 13)? 2 3 5 8 Reveal answer Fill a bubble to check yourself B Correct answer Explanation Aluminum (atomic number 13) has electron configuration 2, 8, 3. The outermost shell (third shell) contains 3 electrons. This follows the 2-n-squared rule for electron shells.