The atomic number of H+ (hydrogen ion) is 1. This is because the atomic number represents the number of protons in the nucleus of an atom. In its neutral state, hydrogen has one proton, and when it loses one electron to form H+, it still has the same number of protons, which is one.
This means that H+ is not a unique element; rather, it is a hydrogen atom that has been ionized by losing its single electron. Therefore, the atomic number remains unchanged at 1.