(i) What characteristic property of nuclear force explains the constancy of binding energy per nucleon (BE/A) in the range of mass number ‘A’ lying 30 < A < 170?(ii) Show that the density of nucleus over a wide range of nuclei is constant-independent of mass number A.



(i) The approximate constancy of BE/A over most of the range is saturation property of nuclear force,In heavy nuclei: nuclear size > range of nuclear force.So, a nuclear sense approximately a constant number of neighbours and thus, the nuclear BE/A levels off at high A. This is saturation of the nuclear force.(ii) To find the density of nucleus of an atom, we have an atom with mass number lets say A. (Here, we are neglecting mass of the orbital electrons)Mass of the nucleus of the atom of the mass number A.= A a.m.u= A × 1.660565 × 10−27 kgLet radius of nucleus is R.Now, we know R0 = 1.1 × 10−15 m 
Density of the nucleusThus, we can see the density of nuclei is independent of the mass number and is constant for all nuclei.