Answer: Difference between mass of nucleus and sum of its nucleons.
- A Difference between mass of nucleus and sum of its nucleons
- B The total mass of all orbital electrons around the nucleus
- C The combined mass of neutrons only, ignoring the protons
- D The ratio of total nuclear charge to total nuclear mass
Correct answer: A. Difference between mass of nucleus and sum of its nucleons
Explanation: Mass defect delta_m = (Z mp + N mn) - M<sub>nucleus</sub>. This mass is converted to binding energy (E = delta_m x c<sup>2</sup>).
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.