group 1 ,(H+), (NH4+) have charges (+1)
group 2, Pb2+, Cu2+,Fe2+ have charges (+2)
group 3, have charges (+3)
group 6, (CO32-), (SO42- ) have charges (-2)
group 7, (OH-), (NO3-) have charges (-1)
* certain ions have various valency:
(Fe2+, Fe3+) , (Pb2+,Pb4+)
