Answer: Emission of an electron from nucleus (neutron to proton).
- A Emission of a helium nucleus consisting of two protons and two neutrons
- B Emission of an electron from nucleus (neutron to proton)
- C Emission of a high-energy photon from a nuclear energy transition
- D Absorption of a neutron by the nucleus from outside
Correct answer: B. Emission of an electron from nucleus (neutron to proton)
Explanation: Beta-minus: neutron converts to proton + electron + antineutrino inside nucleus. Atomic number increases by 1.
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.