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.
Nuclear equations, conservation and beta decay 20(m)–(o)
Question 1
Complete ¹⁴₆C beta-minus decay and state why an antineutrino is required.
Check the model response
¹⁴₆C → ¹⁴₇N + ⁰₋₁e + ν̄ₑ. The antineutrino shares variable energy and momentum so both are conserved across the continuous beta spectrum.
repair
2. Repair the common breaks
Use only the correction matching an error, then retry the corresponding diagnostic.
Nuclear equations, conservation and beta decay 20(m)–(o)
Check this idea
Misconception: Only nucleon number must balance.
Repair: Charge, mass-energy and momentum must also be conserved.
Check this idea
Misconception: The beta electron alone receives a fixed decay energy.
Repair: Electron, recoil and antineutrino share energy and momentum.
worked example
3. Follow six worked models
Follow how each solution uses evidence, corrected data, risk criteria, conservation or the binding-energy curve.
Nuclear equations, conservation and beta decay 20(m)–(o)
Model 1
Balance ¹⁴₇N + ⁴₂He → ¹⁷₈O + X.
Check the model response
Conserving nucleon number gives A = 1 and charge gives Z = 1, so X is ¹₁H. Mass-energy and momentum must also be conserved.
guided practice
4. Guided practice
Use each hint only to select the correct nuclear number, population relation, radiation property or energy comparison.
Nuclear equations, conservation and beta decay 20(m)–(o)
Question 1
In beta-minus decay, state changes in A and Z.
Hint: A neutron becomes a proton.
Check the model response
A is unchanged and Z increases by one.
independent practice
5. Independent practice
Solve without repair notes and state background, conservation, exposure and curve assumptions.
Nuclear equations, conservation and beta decay 20(m)–(o)
Question 1
Write and check a nuclear equation and explain antineutrino evidence.
Check the model response
Conserve A and charge explicitly, then conserve mass-energy and momentum. A continuous beta energy spectrum contradicts fixed two-body energy sharing; an antineutrino carries the missing variable energy and momentum.
Practice exit check
6. Practice assessment
Use this as extra closed-book practice, then complete the separate recorded assessment in your plan.
Nuclear equations, conservation and beta decay 20(m)–(o)
Question 1
Complete ²¹⁰₈₄Po → ²⁰⁶₈₂Pb + X and name conserved quantities.
Check the model response
X = ⁴₂He. Nucleon number, charge, mass-energy and momentum are conserved.
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.
Nuclear equations, conservation and beta decay 20(m)–(o)
Question 1
Why does beta-minus decay keep nucleon number unchanged?
Check the model response
A neutron changes into a proton; the total number of nucleons is unchanged.