What is the ammonium ion represented as?

The ammonium ion is represented as NH4+. This ion is a positively charged polyatomic ion formed when ammonia (NH3) gains a proton (H+). In this process, the ammonia molecule, which is neutral, becomes positively charged due to the addition of the hydrogen ion, resulting in NH4+, known as the ammonium ion.

Ammonium is commonly found in various chemical contexts, particularly in solutions where it can act as a weak base. Its formation is also crucial in biological systems, especially in the nitrogen cycle, where it serves as a key nutrient for plants.

The other representations listed do not correspond to the ammonium ion. NH3 refers to ammonia, which is the neutral form. NO3- is the nitrate ion, a negatively charged ion that contains nitrogen and oxygen. N3- is the azide ion, another negatively charged ion with a different structure and significance.