|Ammonium, NH4+||Hydroxide, OH-|
|Calcium, Ca2+||Nitrate, NO3-|
|Sodium, Na+||Carbonate, CO32-|
|Lead, Pb2+||Sulfate, SO42-|
The formulae of compounds containing polyatomic ions are worked out in a similar way to single atom ions. Except when there is more than one polyatomic ion, then its formula is written inside brackets.
Calcium hydroxide contains Ca2+ and OH- ions:
Deduce the formula for sodium carbonate.
Sodium carbonate contains Na+ and CO32- ions:
Deduce the formula for lead nitrate.
Lead nitrate contains Pb2+ and NO3- ions: