1.15 deduce the number of outer electrons in a main group element from its position in the periodic table

Elements in group one have 1 electron on their outer shell
Elements in group two have 2 electrons on their outer shell
Elements in group three have 3 electrons on their outer shell
Elements in group four have 4 electrons on their outer shell
Elements in group five have 5 electrons on their outer shell
Elements in group six have 6 electrons on their outer shell
Elements in group seven have 7 electrons on their outer shell
Elements in group eight have 8 electrons on their outer shell

Therefore, all you need to do to find the number of outer electrons an element has is work out which group it is n the periodic table.