More Details on Variability of Ions

If is a transition metal then there may be several choices for the oxidation number of that metal. Such oxidation number is typically expressed in the name of a compound using brackets and roman numerals.

Exceptions

The exception transition metals are: Ag and Zn , their oxidation number does not change, these two can only form one type of ion: Ag⁺ and Zn²⁺.