AQA GCSE Combined Science: Trilogy Physics Paper 1 (Higher), 2020: Question 2
11 marks · Standard Demand difficulty · Extended Answer
Determine mass and atomic numbers in alpha and beta decay equations, identify gamma radiation, and explain differences between alpha, beta and gamma radiation.
Practise this questionQuestion
Question text
02 Different radioactive isotopes emit different types of nuclear radiation.
A polonium-210 (Po) nucleus emits an alpha particle (α) and turns into a
lead (Pb) nucleus.
This can be represented by the equation:
02.1 What is the value of A in the equation?
[1 mark]
Tick ( ) one box.
A = 206 A = 208 A = 210 A = 211
02.2 What is the value of Z in the equation?
[1 mark]
Tick ( ) one box.
Z = 80 Z = 82 6 Z = 85 Z = 86
02.3 A strontium-89 nucleus (Sr) emits a beta particle (β) and turns into an
yttrium nucleus (Y).
This can be represented by the equation:
What are the values of A and Z in the equation?
[2 marks]
A =
Z =
02.4 Gamma radiation is another type of nuclear radiation.
What does gamma radiation consist of?
[1 mark]
Tick ( ) one box.
High energy neutrons
Electromagnetic waves
Particles with no charge
Positively charged ions 7
02.5 Explain the differences between the properties of alpha, beta and gamma radiations.
[6 marks]
Mark scheme
Show the mark scheme
AO /
Question Answers Extra information Mark
Spec. Ref.
02.1 A = 206 1 AO2
6.4.2.2
02.2 Z = 82 1 AO2
6.4.2.2
02.3 89 numbers must be in this order 1 AO2
6.4.2.2
39 1
02.4 electromagnetic waves 1 AO1
6.4.2.1
AO /
Question Answers Mark
Spec. Ref.
Level 3: Relevant points (reasons/causes) are identified, given in
02.5 5–6 AO1
detail and logically linked to form a clear account.
6.4.1.2
6.4.2.1
Level 2: Relevant points (reasons/causes) are identified, and there 3–4
6.4.2.2
are attempts at logical linking. The resulting account is not fully
clear.
Level 1: Points are identified and stated simply, but their relevance 1–2
is not clear and there is no attempt at logical linking.
No relevant content 0
Indicative content
alpha radiation
• an alpha particle is the same as a helium nucleus
• alpha is the least penetrating
• alpha is stopped by paper or skin
• alpha has the shortest range in air
• alpha will travel a few cm in air
• because alpha is most ionising
• because alpha has a charge of +2
beta radiation
• a beta particle is an electron (emitted from the nucleus)
• beta penetrates less than gamma and more than alpha
• beta is stopped by a thin sheet of aluminium
• beta has a shorter range than gamma
• beta will travel up to 1m in air
• because beta is more ionising that gamma and less ionising
than alpha
• because beta has a charge of -1
gamma radiation
• gamma radiation is an electromagnetic wave
• gamma is the most penetrating
• gamma is reduced/stopped by several cm of lead or thick
concrete
• gamma has the largest range in air
• gamma will travel very large distances in air
• because gamma is least ionising
• because is uncharged
to access level 3 the answer should compare alpha, beta and
gamma radiation and provide some explanation of their properties
Total 11
How to answer it
Radioactive Isotopes: Alpha, Beta and Gamma
You need to read nuclear equations, use conservation of mass number and atomic number, identify gamma radiation, and compare the properties of alpha, beta and gamma radiation in a clear, linked explanation.
Part (a) 02.1 — Find A in the alpha decay equation
✅ Correct answer
A = 206
1 mark for the correct mass number only.
💡 Key knowledge
- An alpha particle is 2 protons and 2 neutrons.
- So it has mass number 4.
- Mass number is conserved in nuclear equations.
🧠 Exam technique
Subtract 4 from the original mass number:
210 − 4 = 206
Always check the question is asking for the mass number, not the atomic number.
Part (b) 02.2 — Find Z in the alpha decay equation
✅ Correct answer
Z = 82
1 mark for the correct atomic number.
💡 Key knowledge
- Alpha decay removes 2 protons from the nucleus.
- Atomic number tells you the number of protons.
- So the atomic number goes down by 2.
❌ Common errors
- Using 4 instead of 2 for the atomic number change.
- Mixing up the atomic number with the mass number.
- Choosing the wrong answer because 82 is the known atomic number of lead.
Part (c) 02.3 — Beta decay of strontium-89
✅ Correct answers
A = 89
Z = 39
2 marks: one for each correct value, in the right place.
📐 Step-by-step
- In beta decay, a neutron changes into a proton.
- The mass number stays the same, so A = 89 .
- The atomic number increases by 1, so 38 → 39 .
- Therefore Z = 39 .
🧠 Exam technique
For beta decay:
- Mass number unchanged.
- Atomic number increases by 1.
The mark scheme says the numbers must be in this order, so write them clearly as A first, then Z.
Part (d) 02.4 — What does gamma radiation consist of?
✅ Correct answer
Electromagnetic waves
1 mark for ticking the correct box.
💡 Key knowledge
- Gamma is a form of electromagnetic radiation.
- It has no mass and no charge.
- It is emitted from the nucleus after alpha or beta decay.
❌ Common errors
- Choosing “particles with no charge” — gamma is not a particle in GCSE terms.
- Choosing neutrons or positively charged ions.
- Forgetting that gamma is a wave, not matter.
Part (e) — Compare the properties of alpha, beta and gamma radiation
What a top answer needs
💡 Key knowledge to include
- Alpha is a helium nucleus: 2 protons + 2 neutrons.
- Beta is an electron emitted from the nucleus.
- Gamma is an electromagnetic wave.
- Alpha is the most ionising and least penetrating.
- Beta is moderately ionising and medium penetrating.
- Gamma is the least ionising and most penetrating.
- Alpha travels only a few cm in air; beta up to about 1 m; gamma travels very far.
- Alpha is stopped by paper/skin; beta by thin aluminium; gamma by thick lead or concrete.
🧠 Exam technique
- To reach the top level, compare all three radiations.
- Don’t just list facts separately — link them with words like whereas, however, and because.
- Include both penetration and ionising power.
- Explain properties using charge and mass where possible.
❌ Common errors
- Saying gamma is a “particle with no charge” instead of an electromagnetic wave.
- Mixing up beta and gamma penetration.
- Forgetting that alpha is a helium nucleus.
- Writing only one radiation in detail and ignoring comparisons.
- Not linking properties to why they happen.
✅ Full-mark style answer
Alpha radiation is the least penetrating because it is a heavy helium nucleus with a charge of +2, so it is strongly ionising and is stopped by paper or skin. Beta radiation is an electron from the nucleus. It is less ionising than alpha and more penetrating, so it can travel further in air and is stopped by a thin sheet of aluminium. Gamma radiation is an electromagnetic wave with no charge and no mass, so it is the least ionising and most penetrating. It can travel very large distances and needs thick lead or concrete to reduce it.
This would score highly because it compares all three types and gives reasons for the differences.
❌ Mark-losing traps for the 6-marker
- Writing just “alpha stops, beta goes further, gamma goes farthest” without explanation.
- Using vague phrases like “strong” or “weak” without saying ionising or penetrating.
- Missing the order: alpha least penetrating, gamma most penetrating.
- Not mentioning that gamma is an electromagnetic wave.
💡 Alpha
Helium nucleus, charge +2, most ionising, least penetrating, stopped by paper/skin.
💡 Beta
Electron from the nucleus, charge −1, medium ionising, stopped by thin aluminium.
💡 Gamma
Electromagnetic wave, no charge, least ionising, most penetrating, reduced by lead or concrete.
Topics
Physics · P4: Atomic Structure
Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Physics Paper 1 (Higher), 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.