What is the formula for ammonia and ammonium, respectively?

The formula for ammonia is NH3, which consists of one nitrogen atom and three hydrogen atoms. This is the widely recognized and standard structure for ammonia, a common molecule found in various chemical contexts, including biology and environmental science.

Ammonium, on the other hand, is a positively charged ion, which is represented as NH4+. In this ion, the nitrogen is bonded to four hydrogen atoms and carries a positive charge due to the addition of an extra proton (H+). This change from ammonia to ammonium results from the protonation of ammonia.

The correct answer highlights the distinction between the neutral ammonia molecule and the positively charged ammonium ion, emphasizing both their chemical formulas and the significance of the charge in their interactions. Understanding these formulas is crucial in areas such as acid-base chemistry and biochemistry, where ammonium ions play important roles in metabolic processes.