Answer: 10 -15 m.
- A 10<sup>-9</sup> m
- B 10<sup>-12</sup> m
- C 10<sup>-10</sup> m
- D 10<sup>-15</sup> m
Correct answer: D. 10<sup>-15</sup> m
Explanation: 1 fermi = 1 femtometre = 10<sup>-15</sup> m, the order of nuclear radii.
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.