Mini PhysicsPart of Mini Education

Focused revision

Atomic and Nuclear Physics revision guide

Use the skill selected by your revision plan. Work in order: understand the idea, study the example, check the common mistake, practise it, then check again in 7 days.

Focused skill

Nuclides and isotopes

1. Explain

Proton number fixes the element; nucleon number is protons plus neutrons. Isotopes share proton number but differ in neutron and nucleon numbers, while ion charge concerns electrons.

2. Model

For ²⁷₁₃Al, protons = 13, neutrons = 14 and a neutral atom has 13 electrons. Aluminium-26 is an isotope because proton number remains 13.

Isotope comparison

Predict
Predict which nuclei represent the same element.
Change
Change neutron number while holding proton number fixed.
Observe
Record nucleon and proton numbers for each nuclide.
Interpret
Identify isotopes by equal proton number and different neutron number.
Limitation
The model is schematic and not a scale picture of nuclei.
Transfer
Classify an unfamiliar pair of nuclides as isotopes or different elements.
Open the activity

3. Practise: concept check

Do isotopes have different proton numbers?

  • No; they differ in neutron number.
  • Yes; changing proton number makes an isotope.
Check the answer and feedback

Correct: No; they differ in neutron number. Changing proton number changes the element itself.

Not yet: Changing proton number changes the element itself.

4. Apply: examiner-style practice

For chlorine-37 with proton number 17, state proton, neutron and electron numbers for a neutral atom and explain isotope identity.

[2 marks]

Self-mark with the mark scheme

Compare your response with each mark point. Select a point only when your response contains that evidence.

Award a mark only when the stated physics matches the mark point. Carry forward a correct method after an arithmetic slip; do not award a bare answer where reasoning is requested.

Mark points

5. Check again in 7 days: return through Your Physics plan after seven days. You will get a different question and cannot complete it early.

Focused skill

Radioactive-emission equations

1. Explain

Nuclear equations conserve total nucleon number A and proton number Z. Alpha has A = 4 and Z = 2, beta-minus has A = 0 and Z = −1, and gamma has A = 0 and Z = 0.

2. Model

In alpha decay, the daughter A decreases by 4 and Z by 2. In beta-minus decay, daughter A is unchanged and Z increases by 1; gamma changes neither.

Nuclear-equation investigation

Predict
Predict daughter A and Z before revealing an emission.
Change
Change emission type while retaining the parent nuclide.
Observe
Record parent, emission and daughter numbers.
Interpret
Check conservation of nucleon and proton number.
Limitation
The model omits decay-energy distributions.
Transfer
Complete an unfamiliar alpha or beta-minus equation.
Open the activity

3. Practise: concept check

May an unbalanced equation still identify the correct decay?

  • No; both total A and total Z must balance.
  • Yes; naming the emission is enough.
Check the answer and feedback

Correct: No; both total A and total Z must balance. Use both conserved totals to check every nuclear equation.

Not yet: Use both conserved totals to check every nuclear equation.

4. Apply: examiner-style practice

Complete alpha decay of radium-226, proton number 88, and beta-minus decay of carbon-14, proton number 6.

[2 marks]

Self-mark with the mark scheme

Compare your response with each mark point. Select a point only when your response contains that evidence.

Award a mark only when the stated physics matches the mark point. Carry forward a correct method after an arithmetic slip; do not award a bare answer where reasoning is requested.

Mark points

5. Check again in 7 days: return through Your Physics plan after seven days. You will get a different question and cannot complete it early.

Focused skill

Half-life calculations

1. Explain

Half-life is the time for undecayed nuclei or activity to halve. In a fixed detector setup, corrected count-rate is proportional to activity and also halves on average.

2. Model

Activity 960 counts/min falling to 120 counts/min has undergone three halvings. If this takes 15 min, half-life is 5.0 min.

Half-life data investigation

Predict
Predict corrected activity after each half-life before running the sample.
Change
Change half-life, initial nuclei and counting interval separately while retaining background controls.
Observe
Record repeated count rates and background at equal time intervals.
Interpret
Subtract background, plot activity, identify successive halvings and distinguish scatter from trend.
Limitation
Finite simulated samples fluctuate and detector efficiency is idealised.
Transfer
Determine half-life from an unfamiliar table or graph and explain random scatter.
Open the activity

3. Practise: concept check

After one half-life has every nucleus lost half its mass?

  • No; about half the original unstable nuclei remain undecayed.
  • Yes; each nucleus is physically cut in half.
Check the answer and feedback

Correct: No; about half the original unstable nuclei remain undecayed. Half-life describes a population or activity, not fractional decay of each nucleus.

Not yet: Half-life describes a population or activity, not fractional decay of each nucleus.

4. Apply: examiner-style practice

A source reads 820 counts/min including 20 background and has half-life 6.0 h. Predict the detector reading after 18 h.

[2 marks]

Self-mark with the mark scheme

Compare your response with each mark point. Select a point only when your response contains that evidence.

Award a mark only when the stated physics matches the mark point. Carry forward a correct method after an arithmetic slip; do not award a bare answer where reasoning is requested.

Mark points

5. Check again in 7 days: return through Your Physics plan after seven days. You will get a different question and cannot complete it early.

Focused skill

Applications and hazards

1. Explain

Choose radioactive sources by half-life, penetrating ability and ionising effect. Minimise exposure using time, distance, shielding and remote handling, and distinguish irradiation from contamination.

2. Model

A medical tracer needs radiation able to leave the body for detection, sufficiently low ionising effect, and a half-life long enough for the procedure but short enough to limit prolonged exposure.

Radiation detection and safety protocol

Predict
Predict which absorber most reduces each emission and identify the background correction.
Change
Change source type, absorber and distance one at a time without direct handling.
Observe
Record repeated source-plus-background and background counts for fixed intervals.
Interpret
Calculate corrected rates and compare penetration using controlled geometry.
Limitation
A simulation cannot reproduce real contamination, dead time or calibration limits.
Transfer
Write an examiner method with time, distance, shielding, background and uncertainty controls.
Open the activity

3. Practise: concept check

Must an irradiated object become radioactive?

  • No; contamination requires radioactive material to be transferred.
  • Yes; any exposure creates a source.
Check the answer and feedback

Correct: No; contamination requires radioactive material to be transferred. Irradiation and contamination are different hazards and controls.

Not yet: Irradiation and contamination are different hazards and controls.

4. Apply: examiner-style practice

Choose a suitable emission for a medical tracer and a sheet-thickness gauge, then justify each choice and state one control.

[2 marks]

Self-mark with the mark scheme

Compare your response with each mark point. Select a point only when your response contains that evidence.

Award a mark only when the stated physics matches the mark point. Carry forward a correct method after an arithmetic slip; do not award a bare answer where reasoning is requested.

Mark points

5. Check again in 7 days: return through Your Physics plan after seven days. You will get a different question and cannot complete it early.

Focused skill

Fission, fusion and nuclear energy

1. Explain

Fission is the splitting of a heavy nucleus into smaller nuclei; fusion is the joining of light nuclei to form a heavier nucleus. Both processes are associated with energy release from nuclear fuel.

2. Model

Classify a process by what happens to the nuclei: one heavy nucleus splitting is fission, while light nuclei joining is fusion. Detailed reactor technology and energy–mass equivalence are outside this O-Level outcome.

Fission and fusion comparison

Predict
Predict whether light nuclei join or a heavy nucleus splits.
Change
Select fission or fusion and compare reactants and products.
Observe
Record the nuclear rearrangement and energy-release indication.
Interpret
Distinguish splitting a heavy nucleus from joining light nuclei.
Limitation
The display does not model reactor engineering or fusion confinement.
Transfer
Explain which process fits an unfamiliar nuclear-fuel description.
Open the activity

3. Practise: concept check

Are fission and fusion ordinary changes of state?

  • No; they are nuclear processes associated with energy release.
  • Yes; they are melting and freezing at high temperature.
Check the answer and feedback

Correct: No; they are nuclear processes associated with energy release. Use nucleus-level definitions and stay inside the syllabus boundary.

Not yet: Use nucleus-level definitions and stay inside the syllabus boundary.

4. Apply: examiner-style practice

State the meanings of fission and fusion and relate both to nuclear-fuel energy release.

[2 marks]

Self-mark with the mark scheme

Compare your response with each mark point. Select a point only when your response contains that evidence.

Award a mark only when the stated physics matches the mark point. Carry forward a correct method after an arithmetic slip; do not award a bare answer where reasoning is requested.

Mark points

5. Check again in 7 days: return through Your Physics plan after seven days. You will get a different question and cannot complete it early.

Focused skill

Atomic composition

1. Explain

An atom contains a small positive nucleus made of protons and neutrons, with negatively charged electrons outside the nucleus. A neutral atom has equal proton and electron numbers.

2. Model

For a neutral atom with 8 protons and 10 neutrons, the nucleus has charge +8 in elementary-charge units, there are 8 electrons outside, and the nucleon count is 18.

Atomic-structure model

Predict
Predict the location and charge of each particle.
Change
Change proton, neutron and electron counts separately.
Observe
Record nuclear composition and net charge.
Interpret
Separate the positive massive nucleus from electrons outside it.
Limitation
The schematic is not drawn to atomic scale.
Transfer
Describe an unfamiliar atom or ion from its particle counts.
Open the activity

3. Practise: concept check

Are electrons part of the positive nucleus?

  • No; electrons are negatively charged and outside the nucleus.
  • Yes; all three particles occupy the nucleus.
Check the answer and feedback

Correct: No; electrons are negatively charged and outside the nucleus. Keep nuclear particles and external electrons in their correct regions.

Not yet: Keep nuclear particles and external electrons in their correct regions.

4. Apply: examiner-style practice

Describe the composition and charges of a neutral atom containing 12 protons and 13 neutrons.

[2 marks]

Self-mark with the mark scheme

Compare your response with each mark point. Select a point only when your response contains that evidence.

Award a mark only when the stated physics matches the mark point. Carry forward a correct method after an arithmetic slip; do not award a bare answer where reasoning is requested.

Mark points

5. Check again in 7 days: return through Your Physics plan after seven days. You will get a different question and cannot complete it early.

Focused skill

Nuclide notation

1. Explain

Nuclide notation ᴬZX identifies element X, nucleon number A and proton number Z. Neutron number is A − Z.

2. Model

In ²³₁₁Na, A = 23, Z = 11 and neutron number = 12. The symbol Na and proton number identify sodium.

Nuclide-notation model

Predict
Predict A and Z from particle counts.
Change
Change proton and neutron numbers separately.
Observe
Record notation and calculate neutron number A − Z.
Interpret
Interpret upper and lower numbers consistently.
Limitation
The symbol placement is conventional rather than spatial.
Transfer
Write and interpret an unfamiliar nuclide symbol.
Open the activity

3. Practise: concept check

Is the upper number A the neutron number?

  • No; A is the total number of protons and neutrons.
  • Yes; subtracting is never required.
Check the answer and feedback

Correct: No; A is the total number of protons and neutrons. Use A − Z to obtain neutron number.

Not yet: Use A − Z to obtain neutron number.

4. Apply: examiner-style practice

Interpret ³⁷₁₇Cl and write the notation for carbon with 6 protons and 8 neutrons.

[2 marks]

Self-mark with the mark scheme

Compare your response with each mark point. Select a point only when your response contains that evidence.

Award a mark only when the stated physics matches the mark point. Carry forward a correct method after an arithmetic slip; do not award a bare answer where reasoning is requested.

Mark points

5. Check again in 7 days: return through Your Physics plan after seven days. You will get a different question and cannot complete it early.

Focused skill

Random and spontaneous decay

1. Explain

An unstable nucleus loses energy by emitting radiation. Decay is random because the next nucleus and exact decay time cannot be predicted, and spontaneous because it needs no external trigger.

2. Model

Two equal one-minute counts may differ even with an unchanged source and detector. Heating, pressure and chemical state do not switch nuclear decay on or off.

3. Practise: concept check

Can ordinary heating stop radioactive decay?

  • No; ordinary conditions do not control nuclear instability.
  • Yes; cooling or heating schedules each decay.
Check the answer and feedback

Correct: No; ordinary conditions do not control nuclear instability. Random does not mean causeless measurement error, and spontaneous does not mean instantaneous.

Not yet: Random does not mean causeless measurement error, and spontaneous does not mean instantaneous.

4. Apply: examiner-style practice

Explain why repeated counts fluctuate while a large sample still follows a predictable decay trend.

[2 marks]

Self-mark with the mark scheme

Compare your response with each mark point. Select a point only when your response contains that evidence.

Award a mark only when the stated physics matches the mark point. Carry forward a correct method after an arithmetic slip; do not award a bare answer where reasoning is requested.

Mark points

5. Check again in 7 days: return through Your Physics plan after seven days. You will get a different question and cannot complete it early.

Focused skill

Alpha, beta-minus and gamma

1. Explain

Alpha is a helium nucleus, beta-minus is a fast electron and gamma is an electromagnetic wave. Alpha is most ionising and least penetrating; gamma is least ionising and most penetrating of the three.

2. Model

Paper absorbs alpha, thin aluminium absorbs beta, and thick lead or concrete reduces gamma intensity. Alpha and beta are charged; gamma is uncharged.

3. Practise: concept check

Is the most penetrating emission also the most ionising?

  • No; gamma is most penetrating while alpha is most ionising.
  • Yes; both orders are identical.
Check the answer and feedback

Correct: No; gamma is most penetrating while alpha is most ionising. Ionising effect and penetration have opposite orders for these three emissions.

Not yet: Ionising effect and penetration have opposite orders for these three emissions.

4. Apply: examiner-style practice

Compare alpha, beta-minus and gamma by nature, charge, ionising effect and penetrating power.

[2 marks]

Self-mark with the mark scheme

Compare your response with each mark point. Select a point only when your response contains that evidence.

Award a mark only when the stated physics matches the mark point. Carry forward a correct method after an arithmetic slip; do not award a bare answer where reasoning is requested.

Mark points

5. Check again in 7 days: return through Your Physics plan after seven days. You will get a different question and cannot complete it early.

Focused skill

Background radiation

1. Explain

Background radiation is ionising radiation present in the environment and detector reading even when the investigated source is absent. Estimate its average count-rate under matched conditions and subtract it.

2. Model

A source-plus-background reading of 92 counts/min and background of 18 counts/min gives a corrected source rate of 74 counts/min.

3. Practise: concept check

Should random background be ignored?

  • No; its average contribution must be estimated and subtracted.
  • Yes; random counts always cancel exactly.
Check the answer and feedback

Correct: No; its average contribution must be estimated and subtracted. Random variation does not make the mean background contribution zero.

Not yet: Random variation does not make the mean background contribution zero.

4. Apply: examiner-style practice

A detector records 510 counts in 5 min with a source and 90 counts in 5 min without it. Determine the corrected count-rate.

[2 marks]

Self-mark with the mark scheme

Compare your response with each mark point. Select a point only when your response contains that evidence.

Award a mark only when the stated physics matches the mark point. Carry forward a correct method after an arithmetic slip; do not award a bare answer where reasoning is requested.

Mark points

5. Check again in 7 days: return through Your Physics plan after seven days. You will get a different question and cannot complete it early.