Question

(b)Why is the number of neutrons greater than the number of protons in stable nuclei that

have an A> 40? Why is this effect more pronounced for the heaviest nuclei?

Answer 1

${Coulomb repulsion grows for progressively heavier nuclei, but nuclear attraction remains about the same, and so BE/A becomes smaller. This is why stable nuclei heavier than A ≈ 40 have more neutrons than protons. Coulomb repulsion is reduced by having more neutrons to keep the protons farther apart.$

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