AT-U2 · Radioactive decay and evidence

Unit scope

Lectures

AT-U2 · Radioactive decay and evidence

AT-03 · AT-U2 · Planned

Radioactive decay and nuclear emissions

ScopeShared
Difficulty2 / 4 · proposed
Time30–35 min · estimated
StatusPlanned

Learning objectives

Describe unstable-nucleus decay and activity; compare alpha, beta, gamma and neutron emissions, penetration and ionisation.

8463 §§4.4.2.1 / 8464 §§6.4.2.1

DfE single-science pp.43–44 / Combined pp.35–36. Evidence checked 30 September–1 October 2026. Skills: WS1.2,1.5,4.2; MS2c.

Needs firstAT-01,WA-08

Explanation

Radioactive decay is a random change of an unstable nucleus. Activity counts decays per second, whereas a detector counts only what it registers. Alpha, beta, gamma and neutron emissions differ in charge, mass and interactions; beta originates in a nuclear process, not from an ordinary electron-shell transition.

Concepts, equations and units: Activity Bq=decays/s; count rate counts/s differs due to detection; alpha helium nucleus, beta electron from nuclear process, gamma EM, neutron uncharged.

Prediction, demonstration and game exercise

Predict, observe, explain

Use stochastic model decay and shielding cards; distinguish emissions from electron-shell events.

Planned learner game exercise

Select shielding/detection for supplied evidence and classify radiation by charge, mass, range and penetration.

Independent practice

Explain decay randomness and interpret three detector/shield cases.

Original practice example · Shared

A source undergoes 300 decays per second. State activity and unit. Must a detector read 300 counts/s?

Show working and model answer

Working / reasoning

Activity is decays/s; detector efficiency, geometry and background affect measured counts.

Answer

300 Bq; no, count rate need not equal activity.

Exit check and success criteria

Alpha/beta/gamma identities and comparisons correct; neutron identified; activity/count rate distinguished.

During practice, compare the prediction with evidence and give an error-specific prompt. The exit item uses a fresh context or fresh values, answered independently.

Misconceptions, practical links and mastery

Check these misconceptions

Beta is an orbital electron ejected by warming; gamma is a massive particle; decay can be timed for one nucleus.

Practical preparation

Simulation/supplied detector data; any school source work follows specialist controls; no RP.

Virtual preparation and revision only. Required hands-on activities and school records remain separate.

Proposed mastery

0: not yet evidenced. 1: supported. 2: independent exit criteria met. 3: successful changed-context transfer. Advance at 2; revisit with fresh retrieval. These are not GCSE grades.

Full lecture page →

AT-04 · AT-U2 · Planned

Balancing nuclear equations

ScopeShared
Difficulty3 / 4 · proposed
Time30–35 min · estimated
StatusPlanned

Learning objectives

Balance A and Z for alpha/beta/gamma decay; explain why gamma changes neither.

8463 §§4.4.2.2 / 8464 §§6.4.2.2

DfE single-science pp.43–44 / Combined pp.35–36. Evidence checked 30 September–1 October 2026. Skills: WS1.2,4.1; MS1b,3c.

Needs firstAT-03

Explanation

A nuclear equation balances nucleon number and charge/atomic-number bookkeeping. Alpha decay lowers A by four and Z by two. Beta-minus changes a neutron into a proton and emitted electron, raising the daughter’s Z by one without changing A. Gamma changes neither.

Concepts, equations and units: A/Z bookkeeping; alpha ⁴₂He, beta ⁰₋₁e; beta-minus neutron→proton in nucleus; element identity changes when Z changes.

Prediction, demonstration and game exercise

Predict, observe, explain

Demonstrate a worked alpha and beta decay; keep nucleon-number balance separate from electric charge notation.

Planned learner game exercise

Place missing daughter/emission tiles in nuclear equations and verify both balances.

Independent practice

Four equation completions plus one explanation of gamma decay.

Original practice example · Shared

A nucleus with A = 210 and Z = 84 emits an alpha particle. Give daughter A and Z.

Show working and model answer

Working / reasoning

A_daughter = 210 − 4; Z_daughter = 84 − 2.

Answer

A = 206, Z = 82.

Exit check and success criteria

Three equations correct and gamma changes neither A nor Z.

During practice, compare the prediction with evidence and give an error-specific prompt. The exit item uses a fresh context or fresh values, answered independently.

Misconceptions, practical links and mastery

Check these misconceptions

Beta emission lowers daughter Z; atomic mass number means electron count; gamma removes a proton.

Practical preparation

No RP; symbolic practice.

Virtual preparation and revision only. Required hands-on activities and school records remain separate.

Proposed mastery

0: not yet evidenced. 1: supported. 2: independent exit criteria met. 3: successful changed-context transfer. Advance at 2; revisit with fresh retrieval. These are not GCSE grades.

Full lecture page →

AT-05 · AT-U2 · Planned

Half-life and random decay data

ScopeShared + Higher net-decline calculations
Difficulty3 / 4 · proposed
Time35–40 min · estimated
StatusPlanned

Learning objectives

Determine half-life from data/graphs; explain aggregate predictability versus individual randomness; H calculate net decline over half-lives.

8463 §§4.4.2.3 / 8464 §§6.4.2.3

DfE single-science pp.43–44 / Combined pp.35–36. Evidence checked 30 September–1 October 2026. Skills: WS1.2,3.4,3.7; MS1c,3d,4a.

Needs firstAT-03; P0 fractions

Explanation

Half-life is the time for the undecayed population or activity to fall to half its value. It describes aggregate behaviour, not a schedule for one nucleus. Correct measured counts for background before estimating a source half-life. Higher calculations distinguish remaining fraction from net decline.

Concepts, equations and units: Half-life in s or labelled time; corrected count rate after background subtraction; H fractions N=N0(½)^n and decline=N0−N, integer n practice.

Prediction, demonstration and game exercise

Predict, observe, explain

Run repeat stochastic populations then plot count rate; compare large versus small samples.

Planned learner game exercise

Choose a half-life and estimate it from noisy model measurements; separate background from source counts.

Independent practice

Read two half-lives; H two remaining/declined fraction problems; estimate range from repeats.

Original practice example · Shared

A source-only count-rate graph falls from 80 to 40 counts/s in 5 minutes. Estimate half-life.

Show working and model answer

Working / reasoning

A halving interval is 5 minutes; compare another halving interval if the graph permits.

Answer

5 minutes.

Exit check and success criteria

Correct graph interval and randomness explanation; H distinguishes remaining from declined proportion.

During practice, compare the prediction with evidence and give an error-specific prompt. The exit item uses a fresh context or fresh values, answered independently.

Misconceptions, practical links and mastery

Check these misconceptions

After two half-lives nothing remains; half-life is half the total decay time; every nucleus decays at the half-life.

Practical preparation

No RP; random-decay model/supplied counts.

Virtual preparation and revision only. Required hands-on activities and school records remain separate.

Proposed mastery

0: not yet evidenced. 1: supported. 2: independent exit criteria met. 3: successful changed-context transfer. Advance at 2; revisit with fresh retrieval. These are not GCSE grades.

Full lecture page →

AT-06 · AT-U2 · Planned

Contamination, irradiation and evidence quality

ScopeShared
Difficulty3 / 4 · proposed
Time30–35 min · estimated
StatusPlanned

Learning objectives

Distinguish contamination/irradiation and their hazards; evaluate precautions and the value of peer-reviewed risk evidence.

8463 §§4.4.2.4 / 8464 §§6.4.2.4

DfE single-science pp.43–44 / Combined pp.35–36. Evidence checked 30 September–1 October 2026. Skills: WS1.5,1.6,3.7,3.8.

Needs firstAT-03,AT-05

Explanation

Irradiation exposes an object to radiation; contamination means radioactive material is on or inside it. Removing an external source ends that irradiation but does not remove deposited material. Risk conclusions need exposure data and sound methods, not just a dramatic source label.

Concepts, equations and units: Contamination radioactive material present; irradiation exposure to radiation; risk depends on radiation, dose, exposure and location.

Prediction, demonstration and game exercise

Predict, observe, explain

Compare external source removed with deposited source remaining; analyse supplied evidence without medical claims.

Planned learner game exercise

Audit lab-scenario cards for distance,time,shielding and containment choices; critique a flawed public claim.

Independent practice

Write two safety explanations and evaluate a study’s method, sample and publication status.

Original practice example · Shared

An external sealed source is removed with no material transferred to the object. Was it contaminated merely by exposure?

Show working and model answer

Working / reasoning

Exposure alone is irradiation; no radioactive material has been deposited in this scenario.

Answer

No; it was irradiated, not contaminated.

Exit check and success criteria

Both definitions correct, precautions matched to mechanism and a substantive evidence limitation identified.

During practice, compare the prediction with evidence and give an error-specific prompt. The exit item uses a fresh context or fresh values, answered independently.

Misconceptions, practical links and mastery

Check these misconceptions

Irradiation always makes an object radioactive; contamination ends when the external source is switched off.

Practical preparation

No RP; only simulated/source-based radiation safety tasks.

Virtual preparation and revision only. Required hands-on activities and school records remain separate.

Proposed mastery

0: not yet evidenced. 1: supported. 2: independent exit criteria met. 3: successful changed-context transfer. Advance at 2; revisit with fresh retrieval. These are not GCSE grades.

Full lecture page →

Area capstone

Sources and full programme

Sources checked 30 September–1 October 2026. Specifications govern content; textbooks supplement it. England has no single prescribed Physics course book. The full planning document includes sourced comparisons of Collins separate Physics and Trilogy books, Hodder/Hachette Physics and Oxford Physics listings, with access/approval limitations.

Download the complete Markdown programme and coverage matrix

A subsection map is proposed coverage. Clause-level educator review, item moderation, model validation and hands-on provision remain release gates. No all-board alignment or exam-board endorsement is claimed.