Answer:
One or more number of species which have same number of atomic number but different mass number are called isotopes.
For example, [tex]^{1}_{1}H, ^{2}_{1}H, ^{3}_{1}H[/tex] are the isotopes of hydrogen.
So here, the atomic number of each of these isotopes is 1 and have different mass number, that is, 1, 2, 3.
