Answer: Iron-56.
- A Hydrogen
- B Iron-56
- C Uranium-235
- D Helium-4
Correct answer: B. Iron-56
Explanation: Iron-56 has the highest binding energy per nucleon (~8.8 MeV/nucleon). Elements near iron are most stable.
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.