A hydrogen atom that has lost an electron is known as a hydrogen ion or a proton. When an electron is removed from the neutral hydrogen atom, the remaining positively charged nucleus, consisting of a single proton, represents the hydrogen ion. It has a positive charge equivalent to the elementary charge (+1e) due to the presence of the proton. Hydrogen ions, or protons, play a crucial role in various chemical and physical processes, particularly in acidic solutions and proton transfer reactions.