Answer:
3.
Explanation:
Sodium chlorate has the formula NaClO3. We know this because sodium is Na, chlorine is Cl, and because of naming rules. When a compound ends in -ate, it has 3 oxygen atoms. This is the naming rule list with chlorine as the example:
perchlorate: 4 O atoms
chlorate: 3 O atoms
chlorite: 2 O atoms
hypochlorite: 1 O atom
