There are two types of monoatomic ions. (Monoatomic ion means the ion contains a single atom.) There are cations like K1+ and anions like Cl1-. There is a different process for naming each type of ion. Naming cations: Cations from the main-group metals are typically named using the element name followed by the word ion. Examples: Metal symbol Element name Ion symbol Cation name Na sodium Na1+ sodium ion Al aluminum Al 3+ aluminum ion Ca calcium Ca2+ calcium ion Cations formed by metals in other groups and the bottom of the main-group can have more than one positive charge. This complicates the naming process. The different charge types must be named differently. The new system uses a Roman numeral after the element name to indicate the charge. . The old system which we will not use, combines the stem for the element name and the endings -ous and -ic. The -ous ending is applied to the cation with the smaller positive charge. The -ic ending is applied to the cation with the higher positive charge. This system gets particularly messy when there are more than two possible cations. You can see why a "new" system was introduced. The trouble is that both systems are around. The old names are on labels everywhere. . Examples: Metal symbol Element name Ion symbol Cation name (new system) Cation name (old system) Fe iron Fe2+ iron (II) ion ferrous ion Fe iron Fe 3+ iron (III) ion ferric ion Sn tin Sn2+ tin (II) ion stannous ion Sn tin Sn4+ tin (IV) ion stannic ion Cu copper Cu1+ copper (I) ion cuprous ion Cu copper Cu2+ copper (II) ion cupric ion