Question

When graphing nuclear binding energy per nucleon vs the number of nucleons in the nucleus, the significance of the peak near iron-56 is

Choose one:

a. if it was possible to make a atomic bomb from iron-56 it would release more energy than even a hydrogen bomb

b. the nuclei heavier than iron release energy when undergoing fission, whereas lighter nuclei can release energy in fusion reactions.

c. Spacecraft can be shielded with iron-56 to protect the astronauts from dangerous radiation

d. isotopes with even numbers of nucleons are the most stable

Answer 1

Peak near iron-56 suggests that this is one of the elements with highest binding energy per nucleon. It means that more amount of external work must be done to make this element undergo either fusion or fission. The elements lighter than iron can undergo fusion by combining with other nuclei, the products of which will have higher binding energy than the parent nuclei. The opposite is true for elements heavier than iron. Naturally, an element always tends towards higher stability. Since iron is already in a stable state, it does not participate in fission or fusion reactions because it is already in the lowest energy state and in order to make it undergo exothermic reactions, an external agent must supply energy.

Therefore option a can not be correct.

Option B is correct because the elements heavier than iron are unstable due to the greater electrostatic forces exerted by the protons in the nuclei as compared to the binding nuclear force, therefore they undergo fission and release energy. In the elements lighter than iron, the binding nuclear force is higher and hence more number of nucleons fuse together and release energy.

option C is not correct because lead is better than iron in shielding radiation.

option D is not related to this question.