1. Carbonate   CO3   PO4   HSO4   OH   Hint Half-n-half Clue   2. Oxide   O   Cl   NH4   PO4   Half-n-half Clue   3. Bisulfate or Hydrogen sulfate   NH4   S   HSO4   O   Half-n-half Clue   4. Phosphate   Cl   NH4   SO3   PO4   Half-n-half Clue   5. Chloride   O   Cl   S   PO4   Half-n-half Clue   6. Nitrate   NH4   NO3   SO4   S   Half-n-half Clue   7. Bisulfite or Hydrogen sulfite   Br   O   OH   HSO3   Half-n-half Clue