What occurs during nuclear fission?

During nuclear fission, the process involves heavy atomic nuclei being split into smaller nuclei. This occurs when a heavy nucleus, such as uranium-235 or plutonium-239, absorbs a neutron and becomes unstable. As a result, the nucleus undergoes a reaction that divides it into two or more lighter nuclei, along with the release of energy, neutrons, and radiation. The energy released during this process is significant, making it the principle behind nuclear reactors and atomic bombs. The splitting of the nucleus also has implications for chain reactions, as the released neutrons can initiate further fission in nearby nuclei. This is a key feature that distinguishes fission from the other processes listed in the options.