1. Hydroxide   HSO4   O   Br   OH   Hint Half-n-half Clue   2. Bisulfate or Hydrogen sulfate   CO3   HSO4   Cl   NH4   Half-n-half Clue   3. Sulfate   O   SO4   Br   NO3   Half-n-half Clue   4. Oxide   Cl   NH4   O   PO4   Half-n-half Clue   5. Bicarbonate or Hydrogen carbonate   SO3   OH   HCO3   I   Half-n-half Clue   6. Ammonium   PO4   SO3   NH4   CO3   Half-n-half Clue   7. Iodide   HSO3   NH4   HSO4   I   Half-n-half Clue