1. Oxide   Br   HCO3   O   SO3   Hint Half-n-half Clue   2. Bisulfate or Hydrogen sulfate   HSO4   NH4   CO3   S   Half-n-half Clue   3. Bisulfite or Hydrogen sulfite   HSO3   I   NH4   CO3   Half-n-half Clue   4. Sulfide   S   SO4   PO4   OH   Half-n-half Clue   5. Phosphate   PO4   HSO4   S   SO3   Half-n-half Clue   6. Sulfate   SO4   HSO3   HCO3   I   Half-n-half Clue   7. Carbonate   CO3   I   Cl   SO3   Half-n-half Clue