But we still need unique names that unambiguously identify each compound. Some compounds have been known for so long that a systematic nomenclature cannot compete with well-established common names. The names of ionic compounds are written by listing the name of the positive ion followed by the name of the negative ion. We therefore need a series of rules that allow us to unambiguously name positive and negative ions before we can name the salts these ions form. Naming Positive Ions Monatomic positive ions have the name of the element from which they are formed.
Some metals form positive ions in more than one oxidation state.
Polyatomic positive ions often have common names ending with the suffix -onium . C 4- carbide Practice Problem 4 Predict the formula of the compound that forms when magnesium metal reacts with nitrogen to form magnesium nitride. At first glance, the nomenclature of the polyatomic negative ions in the table above seems hopeless. There are several general rules, however, that can bring some order out of this apparent chaos. The -ite ending indicates a low oxidation state.