Do Na2O have a Roman numeral?

Answer 1

No, Na2O does not have a Roman numeral. When we talk about sodium oxide (Na2O), we are dealing with sodium and oxygen. We know that sodium has a +1 oxidation state in nearly everything it reacts with. You can pretty much bet on it. As it is essentially always going to combine in this +1 oxidation state, there is no need to differentiate that oxidation state from another one, which is what Roman numerals do.

Oxygen has (almost always) a -2 oxidation state, and that means it takes two +1's to balance with a -2. Sodium, with its +1 oxidation state, will combine in a two-to-one ratio with oxygen, with its -2 oxidation state, to make the oxide.