Revered Members,
Binding energy for lighter nuclei is large and for heavier nuclei BE is less. Why?
I know BE is the energy needed to bind protons and neutrons in a nucleus. Also it can be defined as the energy that must be supplied to disrupt the nucleus into constituent protons and neutrons.
Take a lighter nuclei which has 3 protons and so ideally the energy needed to bind these 3 protons should be less when compared with the energy needed to bind 82 protons(say) in a heavier nuclei . So, why BE is less for heavier nuclei than lighter nuclei?

 

HERE's a nice Wiki on 'binding energy' which shows a graph of binding energy versus nucleons, and there is an exponential increase up to about 60 nucleons, then a slow taper.