Respuesta :
atomic mass deals with the number of protons and neutrons added together, atomic number deals with protons only, though isotopes can be explained like this, say you had a hydrogen atom it's one proton and one electron if you add a neutron to it, the hydrogen becomes Deuterium which is a isotope of hydrogen it's the same atom just a neutron added to it for a different atomic mass if only slightly changed
Atomic mass is the sum of proton and neutrons
Atomic number is just number of protons
Isotopes of elements have same atomic number but different atomic mass due to difference in number of nuetrons
