Final answer:
When charges cancel out for transition metals in ionic compounds, you do not need to add Roman numerals.
Step-by-step explanation:
When dealing with transition metals that have variable charges, the Stock system is used to specify the ionic charge of the metal when naming compounds. In this system, Roman numerals are added in parentheses after the metal's name to indicate the charge on the cation. For example, Fe(II) represents iron with a +2 charge, and Fe(III) represents iron with a +3 charge.
However, if the charges cancel out in a compound, you do not need to add roman numerals. This usually happens when the transition metal forms a compound with a nonmetal that has a fixed charge. In such cases, the name of the cation will be the same as the element's name. For example, in the compound CuCl2, the copper ion has a +2 charge, but we do not need to indicate it with a roman numeral because the charges cancel out. So the answer to your question is: No, you do not add Roman numerals when the charges cancel out for transition metals.
Overall, when naming ionic compounds with transition metals, the addition of roman numerals depends on the presence and magnitude of the charge on the cation.