Nuclear physics: decay, reactions and binding
Key idea: Separate random single-nucleus behaviour from population laws, conserve every required quantity in reactions, and explain released energy through increased binding rather than disappearing mass.
Before you start: Quantum Physics objective chainMeasurement objective chain
By the end, you can
- Interpret nuclear structure, nuclides, random decay and radiation measurements.
- Evaluate radioisotope applications and hazards from physical properties.
- Balance nuclear reactions and use conservation to explain antineutrino evidence.
- Connect mass defect, binding energy and the binding-energy curve to fusion and fission.
Starting-point self-check
1. Check your starting point
Attempt all six groups without notes and mark the first structure, decay, risk, conservation, binding or curve decision you cannot justify. Use the recorded topic diagnostic above when you want scoring and a personalised repair plan.
Mass defect and binding energy 20(p)–(s)
Question 1
Separated nucleons exceed a nucleus by 0.010 u. Find binding energy using 931.5 MeV per u.
Check the model response
Mass defect is 0.010 u and binding energy is 9.315 MeV; the bound system has lower mass-energy.
repair
2. Repair the common breaks
Use only the correction matching an error, then retry the corresponding diagnostic.
Mass defect and binding energy 20(p)–(s)
Check this idea
Misconception: Mass defect means matter vanishes.
Repair: The bound system's lower mass represents released binding energy.
Check this idea
Misconception: Higher binding energy means a less stable nucleus.
Repair: Greater binding energy per nucleon generally means nucleons are more tightly bound.
worked example
3. Follow six worked models
Follow how each solution uses evidence, corrected data, risk criteria, conservation or the binding-energy curve.
Mass defect and binding energy 20(p)–(s)
Model 1
Eight protons and eight neutrons total 16.1280 u; nucleus mass is 15.9905 u. Find mass defect and binding energy.
Check the model response
Δm = 0.1375 u and E = Δmc² = 128 MeV, or 8.0 MeV per nucleon.
guided practice
4. Guided practice
Use each hint only to select the correct nuclear number, population relation, radiation property or energy comparison.
Mass defect and binding energy 20(p)–(s)
Question 1
Mass defect doubles. State binding-energy factor.
Hint: Keep units consistent.
Check the model response
It doubles because E = Δmc².
independent practice
5. Independent practice
Solve without repair notes and state background, conservation, exposure and curve assumptions.
Mass defect and binding energy 20(p)–(s)
Question 1
Define mass defect and binding energy, use E = mc² and describe the binding-energy-per-nucleon curve.
Check the model response
Mass defect is separated-nucleon mass minus nuclear mass. Its energy equivalent is the binding energy. Binding energy per nucleon rises rapidly for light nuclei, peaks near iron and declines slowly for heavy nuclei.
Practice exit check
6. Practice assessment
Use this as extra closed-book practice, then complete the separate recorded assessment in your plan.
Mass defect and binding energy 20(p)–(s)
Question 1
A 12-nucleon nucleus has total binding energy 90 MeV. Find binding energy per nucleon and interpret it.
Check the model response
7.5 MeV per nucleon; it measures average energy needed per nucleon to separate the nucleus, not energy stored by each independent nucleon.
Re-test practice
7. Delayed re-test practice
Return after at least three days and solve these fresh contexts without reopening earlier responses. The recorded plan enforces the delay and uses a separate re-test family for selected-response skill-group evidence.
Mass defect and binding energy 20(p)–(s)
Question 1
Where is binding energy per nucleon greatest approximately?
Check the model response
Near medium-mass iron-region nuclei.