Question

What are the respective formulas for iron (II) oxide and carbon tetrachloride?

Answer 1

Here we have an ionic compound and molecular compound, the latter is easy, remember prefixes for the elements and it usually isn't too far off.
However, for the latter you must know:
1. Iron (II) is a cation of $2+$ charge
2. Oxide is an anion of $2-$ charge
Thus, they cancel each other out to form the compound above!