A positively charged ion does not have the same mass as its neutral atom. It has a slightly lower mass.
When an atom loses one or more electrons to become a positively charged ion (cation), it loses negatively charged particles. Since electrons have a very small mass compared to protons and neutrons, the loss of electrons does not significantly affect the overall mass of the ion.
The mass of an ion is primarily determined by the protons and neutrons in its nucleus. When an atom loses an electron, the number of protons remains the same because the positive charge of the nucleus is balanced by the remaining electrons. However, the number of electrons decreases, resulting in a net positive charge.
Since the mass of electrons is negligible compared to protons and neutrons, the mass of a positively charged ion is slightly lower than that of its neutral atom, specifically by the mass of the lost electrons. The difference in mass is generally very small and is typically not significant for most practical purposes.