Which is the most stable nucleus?

Why the number of neutrons should be equal to the number of protons for a nucleus to be stable?

• what happens if the neutron proton ratio is greater than 1?What is the role of neutrons in the stability of nucleus?

• Answer:

  The most stable element is ferrous in which 26 protons and 30 neutrons are present. Those elements in which equal number of protons and neutrons, an example Lithium, is comparatively less stable than ferrous. The problem is, protons being like charged they must repel themselves and so the nucleus must be broken. But, the exchange interaction using mesons between the nucleons (protons and neutrons) generates the attractive nuclear force, which is the strongest force so far observed in the universe. Being neutral, neutrons will not go against this attractive force. So there comes the possibility of greater stability as neutron number is little bit more than the proton number. As the difference between the numbers of neutrons and protons become more and more as in the case of heavier elements such uranium the stability gets decreased. So, it gives the chance for fission reaction. Meson is solely responsible for the existence of nuclear force. This was suggested by Yukawa.