1. Oxide   Cl   OH   O   SO3   Hint Half-n-half Clue   2. Chloride   Cl   NO3   I   HCO3   Half-n-half Clue   3. Nitrate   SO4   HSO3   HCO3   NO3   Half-n-half Clue   4. Hydroxide   HCO3   NH4   OH   I   Half-n-half Clue   5. Bisulfite or Hydrogen sulfite   O   NO3   HSO3   NH4   Half-n-half Clue   6. Sulfide   I   Br   S   NH4   Half-n-half Clue   7. Ammonium   CO3   NH4   I   SO4   Half-n-half Clue