please correct me if im wrong, but valency i understand to be the ability to lose or gain electrons?
Now, when you look at your periodic table, you have the 8 main groups (columns).
1A - +1
2A - +2
3A - +3
4A - +/- 4 (this one we were told is tricky)
5A - - 3
6A - -2
7A...