Common polyatomic ions and their charges
| Name of ion | Formula of ion |
| Ammonium | NH4+ |
| Acetate | C2H3O2– |
| Bicarbonate (also called hydrogen carbonate) | HCO3– |
| Carbonate | CO32- |
| Cyanide | CN– |
| Hydroxide | OH– |
| Nitrate | NO3– |
| Nitrite | NO2– |
| Phosphate | PO43- |
| Sulfate | SO42- |
| Sulfite | SO32- |
Greek prefixes for naming hydrates and binary molecular compounds
| Prefix | Number |
| mono- | 1 |
| di- | 2 |
| tri- | 3 |
| tetra- | 4 |
| penta- | 5 |
| hexa- | 6 |
| hepta- | 7 |
| octa- | 8 |
| nona- | 9 |
| deca- | 10 |