Ammonium

The ammonium (more obscurely: aminium) cation is a positively charged polyatomic cation with the chemical formula NH4+. 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).

Read more about Ammonium:  Acid Base Properties, Ammonium Salts, Structure and Bonding, Organic Ammonium Ions, Biology, Ammonium Metal