If a class X can be hydronated to Xium ions the class Xium ions commonly includes the derivatives formed by the replacement of the added @H02904@ with a hydrocarbyl group. Aminium ions form an exception, made possible by the availability of the class name ammonium ions.
formed by hydronation of an amine . 'Non-quaternary ammonium ions' is a synonymous term, e.g. prolinium, ,
See also: onium compounds
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1316 (https://doi.org/10.1351/pac199567081307)