NH4 is called ammonium because it is a positively charged polyatomic ion that forms when ammonia (NH3) gains a proton (H+). This process is known as protonation. The resulting ion, NH4+, is named ammonium to distinguish it from the neutral ammonia molecule.
The term ‘ammonium’ comes from the root word ‘ammonia,’ which itself is derived from the name of the ancient Egyptian god Amun. The suffix ‘-ium’ is commonly used in chemistry to denote a cationic species. Therefore, when ammonia gains a proton, it becomes ammonium, indicating its positive charge.
Ammonium ions are commonly found in various chemical compounds and play a significant role in many biological and industrial processes. For example, ammonium salts are widely used in fertilizers, and ammonium ions are essential in the nitrogen cycle, which is crucial for plant growth.