Answer: 100.
- A 50
- B 100
- C 200
- D 400
Correct answer: B. 100
Explanation: 15 years = 3 half-lives, so 800·(1/2)³ = 800/8 = 100 atoms.
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.