Identify the kinds of ions that form each ionic compound

Ionic compounds are formed by a positive ion called cation and a negative ion called anion.

I will show you some examples:

NaCl is formed by the cation Na+  and the anion Cl -

CaF2 is formed by the cation Ca 2+ and the anion F -

Li2O if formd by the cation Li + and the anion O 2-.

To tell that you use the oxidation number of each element. I did it this way

Ca F2 => Ca has oxidation number 2+ and F has oxidation number 1- then the ions have that very same charge number.

The answer is c. 320 g