The previous table demonstrates some naming trends for polyatomic ions. Series of oxoanions (containing oxygen) are named according to the oxidation number of the non-oxygen atom. A general series starts with the oxyanion with the highest oxidation state and contains the prefix "per-" and the suffix "-ate." As the oxidation number decreases the series proceeds to a polyatomic ion with the suffix "-ate," then to a polyatomic ion with the suffix "-ite," and finally to a polyatomic ion with the prefix "hypo-" and the suffix "-ite." A polyatomic ion with the prefix "per-," for example, shows that the non-oxygen atom has a higher oxidation number than a polyatomic ion in the same series with the suffix "-ite." When these ions are in compounds, the names change: the suffix "-ate" becomes "-ic," and the suffix "-ite" becomes "-ous."
Monatomic ions generally retain names similar to the atoms from which they are formed. Cations are named by adding the word "ion" after the name of the atom. Cations that always have the same oxidation state include the alkali metals (+1), the alkaline earth metals (+2), zinc (+2), cadmium (+2), and aluminum (+3). In the case of elements that may have more than one oxidation state, the name of the element is followed by a Roman numeral in parentheses indicating the oxidation state. These elements may also have common names following the pattern of naming the polyatomic
ions. Each element has a stem to which the endings "-ic" (higher oxidation state) and "-ous" (lower oxidation state) are attached. Stems not related to the English name of the element include "cupr-" (copper), "ferr-" (iron), "plumb-" (lead), and
