Question

Binding energy curve........why does Binding energy decrease towards the end of the curve????

Answer 1

Nuclear force has a property of saturation.. because of this, as the atomic number increases, the nuclear force doesn't increase proportionally, but the coulombs repulsion increases.. this kinda gives you an idea.. why as you go towards heavier nuclei, the nucleus tends to be unstable, ergo lesser binding energy!

Answer 2

In a nucleus there are two competing forces:
the strong interaction which is attractive
the coulomb interaction which is repulsive

For a nucleus to exist the net force on all the nucleons must be zero - the attractive forces must balance out the repulsive forces.

The strong nuclear force is a short-range attractive force and so can only interact over a few nucleon diameters.
As the nucleus gets bigger a nucleon cannot necessarily feel the strong nuclear attractive force from all the other nucleons in the nucleus.

On the other hand the coulomb interaction is a long range repulsive force and so all the protons in a nucleus can feel the repulsive force from all the other protons in nucleus.

Nature tries to dilute the coulomb repulsion by adding more and more neutrons into the nucleus (large nuclei have more neutrons than protons) but this makes the nucleus less stable (lower binding energy per nucleon).
Eventually the addition of neutrons does not fully work and so all very large nuclei are unstable - the coulomb interaction wins.

Answer 3

Thanks a lot @Mashy and @Farcher ..........!