by using a periodic table? My teacher taught us a theory, but I didn't quite get it. :S
-
By looking at the columns.
Column 1, 2 & 3 want to have +1, +2 and +3 charges in that order.
Column 6 & 7 want to have -2 and -1 charges.
Dont count your transition metals in the d block (middle.) These charges are only determined by what other element they are bonded to. Also columns 4 and 5 because they elements form covalent bonds and don't want to have a charge.
Column 1, 2 & 3 want to have +1, +2 and +3 charges in that order.
Column 6 & 7 want to have -2 and -1 charges.
Dont count your transition metals in the d block (middle.) These charges are only determined by what other element they are bonded to. Also columns 4 and 5 because they elements form covalent bonds and don't want to have a charge.