The atomic number of an element represents the number of protons in the nucleus of an atom. However, when we refer to a hydrogen ion, it means that the hydrogen atom has gained or lost electrons, resulting in a charged particle.
Hydrogen ion can refer to two different scenarios:
Hydrogen cation (H+): When a hydrogen atom loses its electron, it becomes a hydrogen cation, indicated as H+. In this case, the hydrogen cation has no electrons, and its atomic number remains 1 because the atomic number is determined by the number of protons. So, the atomic number of a hydrogen cation (H+) is still 1.
Hydride ion (H-): In certain chemical compounds, hydrogen can gain an extra electron, forming a negatively charged ion called a hydride ion (H-). In this case, the hydride ion has one additional electron compared to a neutral hydrogen atom, but its atomic number remains 1 because it still contains one proton. Therefore, the atomic number of a hydride ion (H-) is still 1.
In both cases, the atomic number of the hydrogen ion remains 1, indicating the presence of one proton in the nucleus.