1. Hydroxide   SO3   HSO3   Br   OH   Hint Half-n-half Clue   2. Nitrate   I   NO3   PO4   HSO4   Half-n-half Clue   3. Bisulfate or Hydrogen sulfate   O   HSO4   NH4   I   Half-n-half Clue   4. Bromide   NH4   Br   SO3   OH   Half-n-half Clue   5. Carbonate   CO3   O   PO4   S   Half-n-half Clue   6. Oxide   HSO3   Cl   O   HSO4   Half-n-half Clue   7. Ammonium   NH4   SO3   Cl   Br   Half-n-half Clue