[2] It is stable enough to exist in normal conditions, but it is generally reactive and used extensively as an electrophile in the nitration of other substances.

The ion is generated in situ for this purpose by mixing concentrated sulfuric acid and concentrated nitric acid according to the equilibrium: The nitronium ion is isoelectronic with carbon dioxide and has the same linear structure and bond angle of 180°.

Historically, the nitronium ion was detected by Raman spectroscopy, because its symmetric stretch is Raman-active but infrared-inactive.

However, dinitrogen pentoxide in liquid or gaseous state is molecular and does not contain nitronium ions.

[6] Addition of one electron forms the neutral nitryl radical, NO2•; in fact, this is fairly stable and known as the compound nitrogen dioxide.