1. Oxide   O   NH4   PO4   S   Hint Half-n-half Clue   2. Bicarbonate or Hydrogen carbonate   Cl   S   O   HCO3   Half-n-half Clue   3. Sulfite   HSO4   PO4   SO3   NH4   Half-n-half Clue   4. Sulfate   Br   SO4   SO3   CO3   Half-n-half Clue   5. Bromide   CO3   NH4   Br   PO4   Half-n-half Clue   6. Sulfide   S   Br   SO3   HCO3   Half-n-half Clue   7. Iodide   OH   I   SO4   HSO4   Half-n-half Clue