Naming compounds using IUPAC system

Question

I'm stuck with this section where we have to name compounds using IUPAC system, for example: why is KIO4 potassium iodate (7) and NaBrO3 sodium bromate (5). i understand how to name it (like potassium iodate) just not the roman numerals which involves the oxidation state, please can someone explain or refer me to a sight? thanks

Answer 1

Here the oxygen has a set oxidation state of -2 and the  potassium has a fixed oxidation state of +1 so iodine is +7 to balance the charge of zero. same situation with sodium bromate oxygen is -2 *3 = -6 and sodium is +1 gives -5 so bromine is +5 to balance the charge.

Answer 2

IUPAC uses Roman numerals to indicate the charge of a transition metal - that is the only time that Roman are unsed.

When is comes to polyatomic ions, there are a few rules to indicate the number of O atoms; however, you have to memorize the root name first.