Answer: 7/8.
- A 7/8
- B 1/8
- C 3/4
- D 1/4
Correct answer: A. 7/8
Explanation: 1 hour = 3 half-lives, so the fraction remaining is (1/2)<sup>3</sup> = 1/8 and the fraction decayed = 1 − 1/8 = 7/8.
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.