## Chemistry: The Science in Context (4th Edition)

To name an ionic compound, we keep the name of the first element as-is. For the second element in the compound, we change its ending to $-ide$. The name of the cation goes first, followed by the name of the anion. There is no need for prefixes because group 1 and group 2 metals normally have fixed oxidation numbers; this also goes for nonmetals in groups 15, 16, and 17. Therefore, there is no ambiguity in how many atoms of a metal combine with how many atoms of the nonmetal, if they belong to these groups on the periodic table. (a) In this compound, the ammonium ion acts like an ion of a single element. We name this compound ammonium sulfide. (b) In this compound, cesium is bonded to chlorine. Its name is cesium chloride. (c) In this compound, tellurium is bonded to fluorine. Its name is tellurium fluoride. (d) In this compound, rubidium is bonded to oxygen. Its name is rubidium oxide.