A positively charged hypervalent ion of the nonmetallic elements. Examples are the methonium ion CH5+, the hydrogenonium ion H3+ and and the hydronium ion H3O+. Other examples are the carbonium, oxonium, sulfonium, nitronium, diazonium, phosphonium, and halonium ions. Onium ions are not limited to monopositive ions; multiply-charged onium ions exist such as the gitonic (proximal) oxonium dication H4O2+ and the distonic oxonium dication H2O+-CH2-CH2-OH2+.
|Considered between 2004 and 2006 but not included in the 2006 PAC submission|
|This is an unofficial draft definition presented for information and comment.|