Answer: Alpha.
- A Alpha
- B Beta
- C Gamma
- D X-rays
Correct answer: A. Alpha
Explanation: Alpha particles are most ionizing (large charge +2, slow speed: they cause intense ionization but are least penetrating).
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.