answer: the atomic mass of these species is different and atomic number remains same.
isotopes are the chemical species of the same element having different number of neutrons.atomic number is equal to the number of protons or electrons present in that element.
atomic number = number of electrons = number of protonsatomic mass is defined as the sum of number of protons and neutrons contained in an atom.
atomic mass = number of protons + number of neutrons
for isotopes, as the number of neutrons differ, the atomic mass also differs.
for example: carbon has 3 naturally occurring isotopes: . the atomic number remains the same but atomic mass differs.
hence, for isotopes, the atomic mass of these species is different and atomic number remains same.