1. Cu   Copper   Chlorine   Potassium   Magnesium   Hint Half-n-half Clue   2. Co   Potassium   Cobalt   Mercury   Copper   Half-n-half Clue   3. Sb   Lead   Chromium   Antimony   Magnesium   Half-n-half Clue   4. Ni   Phosphorus   Mercury   Magnesium   Nickel   Half-n-half Clue   5. Ar   Silicon   Argon   Lead   Phosphorus   Half-n-half Clue   6. I   Barium   Manganese   Chlorine   Iodine   Half-n-half Clue   7. Ca   Tin   Manganese   Calcium   Nitrogen   Half-n-half Clue