Retrieval Practice
Atomic Structure & Nuclear Stability — AQA A-Level Physics
Q1. State the three particles that make up an atom and give their charges.
- Proton (charge +1.60 × 10⁻¹⁹ C), neutron (charge 0), electron (charge −1.60 × 10⁻¹⁹ C).
- Protons and neutrons are in the nucleus; electrons orbit the nucleus.
Q2. Define specific charge and state its units.
- The ratio of the total charge of a particle to its mass.
- Units: C kg⁻¹.
Q3. State the specific charge of an electron and a proton.
- Electron: 1.76 × 10¹¹ C kg⁻¹.
- Proton: 9.58 × 10⁷ C kg⁻¹.
- Both are on the data sheet.
Q4. What do A and Z represent in ᴬ_Z X notation?
- A = nucleon number (total protons + neutrons).
- Z = proton number (total protons).
- Number of neutrons = A − Z.
Q5. Define isotopes.
Nuclei that have the same number of protons but different numbers of neutrons.
Q6. Describe how the strong nuclear force varies with nucleon separation.
- Below 0.5 fm: repulsive.
- Between 0.5 and 3.0 fm: attractive, with maximum attraction at about 1.0 fm.
- Above 3.0 fm: zero.
Q7. State two differences between the strong nuclear force and the electrostatic force between protons.
(1) The strong force has a short range (0.5–3.0 fm); the electrostatic force has a much longer range. (2) The strong force acts equally on all nucleon pairs; the electrostatic force only acts between charged particles (protons).
Q8. Write the general equation for alpha decay.
- ᴬ_Z X → ᴬ⁻⁴_(Z−2) Y + ⁴₂α.
- Nucleon number decreases by 4, proton number decreases by 2.
Q9. Write the general equation for beta-minus decay.
- ᴬ_Z X → ᴬ_(Z+1) Y + ⁰₋₁β + ⁰₀ν̄ₑ.
- Proton number increases by 1, nucleon number unchanged.
Q10. Write the general equation for beta-plus decay.
- ᴬ_Z X → ᴬ_(Z−1) Y + ⁰₊₁β + ⁰₀νₑ.
- Proton number decreases by 1, nucleon number unchanged.
Q11. What evidence supports the existence of neutrinos?
- Beta particles have a continuous range of energies.
- If only the beta particle were emitted, conservation of energy requires a single discrete energy.
- The continuous spectrum shows energy is shared with an unseen particle — the neutrino.
Q12. Which type of neutrino is emitted in (a) β⁻ decay and (b) β⁺ decay?
(a) Anti-electron neutrino (ν̄ₑ). (b) Electron neutrino (νₑ).