Answer: Atomic electron absorbed by nucleus (p + e⁻ → n + neutrino).
- A An electron being emitted directly from inside the nucleus
- B Atomic electron absorbed by nucleus (p + e⁻ → n + neutrino)
- C A positron being emitted from the nucleus instead of absorbed
- D A gamma ray photon emitted following nuclear excitation
Correct answer: B. Atomic electron absorbed by nucleus (p + e⁻ → n + neutrino)
Explanation: Electron capture: inner atomic electron captured by nucleus. Proton + electron → neutron + electron neutrino. Competes with positron emission.
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.