The process of two light nuclei joining to form a heavier nucleus is called

• A. Fission
• B. Decay
• C. Fusion
• D. Ionization

Answer: (C)

Fusion is the process where two light nuclei join to form a heavier nucleus, releasing energy in the process. This happens because the resulting nucleus has a larger binding energy per nucleon, so some mass is converted to energy (mass defect) in the reaction. For light elements, moving toward a more tightly bound nucleus releases energy, which is why fusion powers stars like the Sun. The other processes describe different nuclear changes: fission splits a heavy nucleus into lighter parts, decay is the spontaneous breakup of an unstable nucleus, and ionization is the removal of electrons from an atom, not changes within the nucleus. So the operation where two light nuclei combine is fusion.