The compounds nitryl fluoride, , and nitryl chloride, , are not nitronium salts but molecular compounds, as shown by their low boiling points (−72 °C and −6 °C respectively) and short nitrogen–halogen bond lengths (N–F 135 pm, N–Cl 184 pm).
Addition of one electron forms the neutral nitryl radical, ; in fact, this is fairly stable and known as the compound nitrogen dioxide.
The related negatively charged species is , the nitrite ion.