# How are metallic compounds named?

May 18, 2015

Metal compounds are typically ionic compounds, in which a metal cation is ionically bonded to an anion. The anion can be from a single element, such as chlorine, or it can be a polyatomic ion such as the hydroxide ion.

The following rules are followed when naming metallic (ionic) compounds.

1. The metal is named first. Its name is unchanged.
2. The anion is named last. If it is from an element, such as chlorine, its name is changed so that one or more syllables are dropped and the ending -ide is added, such as chloride.
3. Many metals, especially transition metals, have more than one possible charge, such as copper. In this case, the charge of the ion is indicated with a Roman numeral, and the name of the metal is given as copper (I) or copper (II), for example.

Examples.
$\text{NaCl}$: sodium chloride
$\text{K"_2"O}$: potassium oxide
$\text{Ca(OH)"_2}$: calcium hydroxide ($\text{OH"^-}$ is the polyatomic hydroxide anion)
${\text{AgNO}}_{3}$: silver nitrate ($\text{NO"_3^-}$ is the polyatomic nitrate anion)
$\text{Cu"_2"O}$: copper (I) oxide (the copper ion has a charge of 1+)
$\text{CuO}$: copper (II) oxide (the copper ion has a charge of 2+)

Notice that Greek prefixes are not used when naming metallic compounds. For example, $\text{K"_2"O}$ is not dipotassium oxide. It is simply potassium oxide.