Isotopes are the elements having same atomic number but different atomic masses eg. C-12,C-13 and C-14 are three isotopes of carbon having same atomic number i.e. 6 but their mass numbers are different which are 12,13 and 14 respectively. The number of protons are same in isotopes but the number of neutrons are different.
No, the masses of isotopes are different, therefore, they do not have somatic masses.