Answer: Converting mass to energy via E=mc² (mass defect).
- A Converting protons directly into neutrons within the nucleus
- B Converting mass to energy via E=mc² (mass defect)
- C Beta emission alone, with no associated mass-energy conversion
- D Fusion of lighter nuclei into a single heavier nucleus
Correct answer: B. Converting mass to energy via E=mc² (mass defect)
Explanation: Fission: heavy nucleus splits into fragments. Product masses total less than reactant masses. Difference (mass defect) appears as energy: E = delta_m × c².
Binding energy per nucleon rises sharply for light nuclei, peaks around iron-56 (the most stable nucleus), then slowly declines for heavier nuclei - which is exactly why fusing light nuclei or splitting heavy nuclei both release energy: each moves the products toward this stability peak.
Concept context
Radioactivity, nuclear reactions, fission, fusion, and binding energy.