Which process involves the release of enormous amounts of energy when small nuclei combine?

• A. Fission
• B. Neutron emission
• C. Spontaneous decay
• D. Fusion

Answer: (D)

Fusion is the process by which light nuclei come together to form a heavier nucleus, and it releases a huge amount of energy. This happens because the resulting nucleus has a higher binding energy per nucleon than the initial ones, so the total mass is slightly reduced (mass defect) and the missing mass becomes energy according to E = mc^2. This energy release is especially large for light elements, and it powers stars and hydrogen bombs. Achieving fusion requires extreme temperatures and pressures to overcome the electrostatic repulsion between positively charged nuclei, creating a plasma where fusion can occur. The other processes involve either splitting heavy nuclei, not combining light ones, or radioactive decay and neutron emission, which do not describe the enormous energy release from fusing light nuclei.