Fission is best described as which process?

• A. The joining of atomic nuclei to form heavier elements
• B. The decay of radioactive material
• C. The emission of photons from excited electrons
• D. The splitting of atoms in a chain reaction to release energy

Answer: (C)

Fission is the splitting of a heavy atomic nucleus into lighter nuclei, usually releasing energy and neutrons. This splitting can trigger a chain reaction because the released neutrons go on to cause further fission in nearby nuclei, releasing more energy. So the description that talks about splitting of a nucleus in a chain reaction to release energy matches fission most closely. The other ideas describe different processes: joining nuclei is fusion, the decay of radioactive material is radioactive decay, and the emission of photons from excited electrons is atomic emission, not nuclear fission.