front 1 Element by itself | back 1 0 |
front 2 Group 1A | back 2 +1 |
front 3 Group 2A | back 3 +2 |
front 4 Halogens | back 4 usually -1 positive with oxygen |
front 5 Monatomic ion | back 5 Ion charge |
front 6 Hydrogen | back 6 +1 with nonmetals -1 with metals |
front 7 Oxygen | back 7 usually -2 -1 in peroxide (O2 -2) |