What is nuclear fission?

• A. The process where a neutron is absorbed by a uranium atom, causing it to split and release energy.
• B. The process of combining two nuclei into a heavier one.
• C. The emission of gamma rays from a stable nucleus.
• D. The decay of a nucleus into lighter elements without neutron capture.

Answer: (A)

Nuclear fission is the splitting of a heavy atomic nucleus into two lighter nuclei, releasing energy in the process. This typically happens when a heavy nucleus like uranium-235 absorbs a neutron, becomes unstable, and splits. The reaction yields fission fragments plus additional neutrons, and those neutrons can trigger more fission in other nuclei, creating a chain reaction. The energy released comes from the difference in binding energy between the original heavy nucleus and the resulting lighter fragments. The other options describe processes that are not fission: fusion is two nuclei joining to form a heavier one, gamma emission is a nucleus emitting gamma radiation without splitting, and radioactive decay without neutron capture refers to alpha or beta decay rather than fission.