The ammonium cation is a positively charged polyatomic ion with the chemical formula NH4+.In the substitutive nomenclature, NH4+ is denoted by the name “azanium”. It is formed by the protonation of ammonia (NH3). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary ammonium cations (NR4+), where one or more hydrogen atoms are replaced by organic radical groups (indicated by R).