Azanium

Although nitrogen N can exist in valence forms that range from a valence of +5 (represented by the nitrate ion NO₃⁻) to a valence of -3 (represented by the ammonium cation, azanium, NH₄⁺), it is the reduced form that is most relevant to the problem at hand.

"In our present work, mixed surfactants of hexadecyl(trimethyl)azanium bromide and sodium dodecyl sulfate were used to mediate the nucleation and growth of CaCO(3) crystals,” scientists in Yangzhou, People's Republic of China report.