Question

Why do we call Ba(NO3)2 barium nitrate, but we call Fe(NO3)2 iron(II) nitrate?

Answer 1

Because iron is a transition metal and could have more than one possible ion charge. The (II) tells us that the charge of iron is +2.

Answer 2

I agree. Barium is not a transitional element hence it can have only one charge ! unlike iron

Answer 3

+2 tells you what the charge of the iron is. Metals like losing electrons