Answer: 14.4 years.
- A 14.4 years
- B 6.93 years
- C 10 years
- D 20 years
Correct answer: A. 14.4 years
Explanation: Mean life τ = T<sub>1/2</sub>/0.693 = 10/0.693 ≈ 14.4 years.
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.