Question

For a nuclear fusion process, suitable nuclei are
(A) Any nuclei
(B) Heavy nuclei
(C) Light nuclei
(D) Nuclei lying in the middle of Periodic table

Answer 1

In nuclear fusion energy is released when the two or more nuclei fuse to form a single nuclei, and the binding energy of the resultant nuclei is greater than that of the two combining nuclei.

Complete step by step answer:
When two or more very light nuclei moving at very high speeds are fused together to form a relatively heavier nucleus, there would be a greater binding energy and a consequent decrease in nuclear mass. This would therefore result in a release of energy. This type of nuclear reaction is known as nuclear fusion, a process opposite to that of nuclear fission.
For fusion, the kinetic energy of the colliding particles must be high enough to overcome the electrostatic Coulomb repulsion. A large kinetic energy implies a high temperature such that fusion energy should be sufficient to provide enough energy to secondary particles to make the process self-sustaining. Unfortunately, the temperature is high and it increases rapidly with atomic numbers. Hence, light nuclei are used in fusion so that the energy released per unit mass of the reaction is comparatively much greater.
Additional information:
Nuclear fission is the splitting of a heavy nucleus under neutron bombardment into lighter radioactive nuclei whose combined mass is less than the mass of the original nucleus. The loss mass is converted into energy. The energy when released in an uncontrolled manner produces destruction, but if released steadily it can be used for peaceful processes as in a reactor.

Note: If heavy nuclei are used for fusion, the Coulombic repulsion will increase the nuclei as the heavy nuclei have more protons. This means more energy is required to fuse the nuclei together. As it lowers the efficiency of the process heavy nuclei are not used.