Justify or criticize although the isobars have same mass numbers their masses are not exactly same" ."

This means that, for Isobars, the number of protons is different but the sum of protons and neutrons is the same. Although Isobars have the same mass number, their masses are not exactly the same. This is because the mass of a neutron is not exactly the same as that of a proton, a neutron is slightly heavier. There are mass spectrometers sensitive enough to measure a hundredth of a mass of the neutron. These devices can be used to differentiate between the masses of Isobars.