Which process describes the joining of two nuclei to form a larger nucleus?

• A. Spontaneous decay
• B. Radioactive decay
• C. Fusion
• D. Fission

Answer: (C)

Fusion is the process where two light nuclei combine to form a heavier nucleus, typically releasing energy when the resulting nucleus has a higher binding energy per nucleon. This occurs in stars under extreme temperatures and pressures that let nuclei get close enough to overcome their electrostatic repulsion. The energy comes from a slight loss of mass during the reaction, with mass difference turning into energy (E = mc^2). Spontaneous decay and radioactive decay describe nuclei emitting particles to reach greater stability, not joining with another nucleus. Fission is the splitting of a heavy nucleus into lighter pieces, the opposite of fusion. So the described process is fusion.