We'll learn how to name ionic compounds that have transition metals in them. The names for transition metal compounds often have roman numerals in them, because the roman numerals indicate the charge on the transition metal. This is because transitional metal elements are able to make a variety of ions with different charge. In order to write the roman numeral for a transition metal compound, we need to work backwards, using the periodic table or a list of polyatomic ions to figure out what charge it has in that particular ionic compound.