We have to calculate (a) the energy needed to remove a proton from a nucleus, and (b) the energy needed to remove a proton from the resulting nucleus. The needed atomic masses are

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(a)

We have to calculate the energy needed to remove a proton from a nucleus. We note that the atomic number of antimony is 51 and therefore an antimony atom has 51 electrons.

The atomic number of is 50 and so a atom contains 50 electrons.

Therefore, the energy required for removing a proton from a nucleus will be

(b)

We have to calculate the energy needed to remove a proton from a nucleus. We note that the atomic number of indium is 49 and so an atom contains 49 electrons.

Therefore, the energy required for removing a proton from a nucleus will be

We note that nucleus contains 50 protons, which is a magic nucleon number. Therefore, nucleus, which requires 10.6 MeV for removing a proton form it, is more stable than nucleus, which requires 5.8 MeV for removing a proton from it.