If you look at the periodic table you’ll noticed a trend. Group one, sometimes called 1A, has hydrogen in it, it’s group (column) has a positive charge. The group (column) next to it Group 2 sometimes called 2A has twice the charge as group 1. Then you skip the transition metals, and then land on group (column) 13. These guys have a charge of +3 typically. Then you have group 14, sometimes called 4A, and it’s weird and it kind of breaks with this trend. Then you have group (column) 15 next to it, sometime called 5A, which now starts to count down in charge, it has a charge of -3.
And each group (column) after that countdown to zero charge, once you have zero charge you know that you’re in the noble gases.
So, nitrogen in group (column) 15, also know as column 5A. This column has for the most part a charge of -3.
Aluminum is in group (column) 13, they have a charge of +3 typically.
I hope that helps.