Why can I change the mass of an atom by adding protons instead of neutrons and still have a different isotope?
Neutrons are subatomic particles with relative mass but no charge while a protons have both mass and positive charge.. Changing the number of neutrons in the nucleus changes the relative mass but not the charge, however adding protons would change both the mass and charge. Since the atomic number of the element is the number of protons in the nucleus, changing the number of protons results in not only a mass change but a change in the atomic number and the “atom” becomes a different element which is not considered an “isotope “of the original element.
