Final answer:
Nuclear fission is the process where heavier nuclei split into lighter, more stable nuclei, releasing a significant amount of energy, often induced by neutron bombardment. It seeks the stability and higher binding energy per nucleon found in mid-range mass numbers.
Step-by-step explanation:
The process of a heavier nucleus splitting to form lighter nuclei is known as nuclear fission. This usually involves heavy nucleoids with mass numbers greater than 92 and occurs when these unstable nuclei decompose into smaller, more stable elements. A massive amount of energy is released during this process. The fission of uranium-235 is a classic example, where the nucleus splits into smaller fragments and several neutrons upon neutron bombardment. Unlike nuclear fusion, which is the combination of lighter nuclei to form heavier ones, fission is the breaking apart of larger nuclei.
It's important to note that nuclear fission can produce a variety of different fragments and is often induced artificially, although some naturally occurring isotopes can spontaneously undergo fission as well. A driving force for nuclear fission is the pursuit for stability and the attainment of a higher binding energy per nucleon, which tends to peak around the mass number of 56.