Final answer:
The fission of heavy nuclei releases energy because it results in products with higher binding energy per nucleon, increasing stability. In contrast, the fission of light nuclei requires an input of energy due to their already high stability, resulting in products with lower binding energy per nucleon. The correct option explaining the release of energy in the fission of heavy nuclei and the requirement of energy for the fission of light nuclei is a) Fission releases energy due to increased stability.
Step-by-step explanation:
Understanding Nuclear Fission
The process of nuclear fission occurs when a heavy nucleus splits into two or more smaller nuclei along with a few neutrons and a large amount of energy. This energy is released because the products of the fission process have a greater binding energy per nucleon (BE/A) than the original heavy nucleus. The concept of binding energy per nucleon is key to understanding why there's a release of energy in the fission of heavy nuclei and why light nuclei require an input of energy for fission.
The reason fission of heavy nuclei releases energy is due to increased stability. Heavy nuclei, such as uranium and plutonium, have lower BE/A compared to medium-mass nuclei. Therefore, when they split into smaller, more stable nuclei with higher BE/A, energy is released. This is explained by the mass-energy equivalence principle which states that mass can be converted into energy. According to Figure 32.21, heavy nuclei might have a BE/A of about 7.6 MeV/nucleon, while the fission products, with a BE/A of about 8.6 MeV/nucleon, lead to a release of about 1 MeV per nucleon.
On the other hand, light nuclei are already relatively stable with higher BE/A, so splitting them into even smaller parts requires an input of energy to overcome that stability. The need for energy input to cause fission in light nuclei arises because the process results in products with a lower BE/A than the original nuclei, hence the fission of light nuclei is not a naturally occurring process and is not advantageous from an energy production standpoint. In conclusion, the correct option that explains why the fission of heavy nuclei releases energy and why energy is required for fission of light nuclei is: a) Fission releases energy due to increased stability.