Answer: 5 days.
- A 3 days
- B 5 days
- C 7.5 days
- D 15 days
Correct answer: B. 5 days
Explanation: 1/8 = (1/2)<sup>3</sup>, so 3 half-lives elapse in 15 days, giving a half-life of 5 days.
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.