Final answer:
Metals in groups 1A, 2A, and 3A have only one oxidation state, so they don't need Roman numerals. Non-metal ions have different names compared to their neutral forms. Noble gases and some other elements do not form ions.
Step-by-step explanation:
Inorganic compounds are named using naming conventions that are specific to the type of compound and its oxidation state. The metals in groups 1A, 2A, and 3A typically do not need Roman numerals because they only have one common oxidation state. For example, group 1A metals, such as sodium (Na) and potassium (K), always have an oxidation state of +1. However, transition metals and group 4A metals can have multiple oxidation states, so we use Roman numerals to indicate the specific oxidation state in their names. For instance, in the compound FeCl2, iron can have an oxidation state of +2, so we write it as iron(II) chloride.
When a non-metal becomes an ion, the ending of its name changes. For example, when chlorine (Cl) becomes an ion, it is called chloride. Similarly, oxygen (O) becomes oxide, and sulfur (S) becomes sulfide when they become ions.
Elements and groups that do not form ions are those that have a full valence electron shell and therefore do not need to gain or lose electrons to achieve a stable configuration. These include the noble gases in group 18 (such as helium, neon, and argon) and some other elements, such as gold, silver, and platinum.