Definition of "onium" [onium]

• Any cation derived by the addition of a proton to the hydride of any element of the nitrogen, chalcogen or halogen families (noun)
• Any organic derivative of these compounds (noun)
• The bound pair of a particle and its antiparticle (noun)

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• "The concept of superelectrophiles thus emerged from my previous studies on superacidic carbocation and onium ion systems."
• "Examples include onium and carboxonium ions, acyl cations, halonium, azonium, carbozonium ions, even certain substituted carbocations and the like."
• "More recently the concept of the "at" - complexes as a counterpart to the "onium" complexes has led to the development of a new chemistry from which have come the sodium tetra phenylborates."