Explanation:
The group 2 ions are in the second column in the periodic table, for example Be, Mg and Ca
The group 3 ions are in the third column in the periodic table, for example B, Al and Ga
It's the same thing for the rest of the groups
Ions either lose or gain electrons to have a full outer shell, just like the noble gases
metal atoms lose electrons from their outer shell to form positively charged ions
From groups 1 to 3 the charge is the same as the group number
Non metals gain electrons on their outer shell to form negatively charged ions
From groups 5 to 7 the charge is 8 subtract the group number
Example: what is the charge for group 6 ions?
8 - 6 = 2, and the charge is negative so 2-
