Final answer:
The statement is True; Roman numerals are used to indicate oxidation states of cations, and Arabic numerals are used to denote the charge of full ions in the nomenclature of coordination compounds.
Step-by-step explanation:
The statement regarding the nomenclature of coordination compounds is True. In the naming of coordination compounds, Roman numerals are indeed used to indicate the oxidation states of cations. For example, iron in its +2 oxidation state is denoted as iron(II). When indicating the charge of the full ion complex, Arabic numerals are used. For instance, a compound with the formula FeCl2 is named iron(II) chloride, and the Roman numeral (II) indicates the oxidation state of the iron cation. Oxidation states are used chiefly for transition metals where multiple charges are possible.
It's important to note that oxidation states and actual charges are the same only for simple ionic compounds. Furthermore, anions in coordination compounds sometimes have special names, and when the metal is part of an anion, its name often ends with the suffix -ate, along with the oxidation state in Roman numerals. For ternary compounds and ionic compounds in general, their formulas should reflect the lowest whole number ratio of atoms, ensuring that positive and negative charges balance.