AQA GCSE Combined Science: Trilogy Physics Paper 1 (Foundation), November 2020: Question 6

11 marks · Standard Demand difficulty · Extended Answer

Balance nuclear equations for alpha and beta decay, identify the nature of gamma radiation, and explain the differences between the properties of alpha, beta, and gamma radiation.

Practise this question

Question

Question text

06 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:

06.1 What is the value of A in the equation?

[1 mark]

Tick ( ) one box.

A = 206 A = 208 A = 210 A = 211

06.2 What is the value of Z in the equation?

[1 mark]

Tick ( ) one box.

Z = 80 Z = 82 22 Z = 85 Z = 86

06.3 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 =

06.4 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 23

06.5 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.

06.1 A = 206 1 AO2

6.4.2.2

06.2 Z = 82 1 AO2

6.4.2.2

06.3 89 numbers must be in this order 1 AO2

6.4.2.2

39 1

06.4 electromagnetic waves 1 AO1

6.4.2.1

AO /

Question Answers Mark

Spec. Ref.

Level 3: Relevant points (reasons/causes) are identified, given in

06.5 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

16 • 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

Nuclear Equations & Properties of Radiation

🧪 WHAT THIS QUESTION TESTS

This question assesses your ability to complete nuclear decay equations for alpha (α) and beta (β) decay by balancing atomic and mass numbers. It also tests your knowledge of the nature of gamma (γ) radiation and requires a structured comparison of the properties (composition, penetrating power, range in air, and ionising power) of all three types of nuclear radiation.

Question 06.1 & 06.2: Alpha Decay of Polonium-210

Balancing Mass and Atomic Numbers in Alpha Decay (2 Marks)

Context Equation: ²¹⁰₈₄Po → ᴬ_Z Pb + α

✅ Correct Answers

06.1: A = 206 [1 mark]

06.2: Z = 82 [1 mark]

📐 Step-by-Step Balancing

An alpha particle is a helium nucleus: ⁴₂He or ⁴₂α.
Mass number (top): 210 = A + 4 → A = 210 - 4 = 206.
Atomic number (bottom): 84 = Z + 2 → Z = 84 - 2 = 82.

💡 Key Knowledge

During alpha decay:

Mass number decreases by 4.
Atomic number (nuclear charge) decreases by 2.

❌ Common Errors

Adding 4 and 2 instead of subtracting them (e.g., choosing A = 214 or Z = 86).
Forgetting that α has a mass of 4 and an atomic number of 2 because they are not written in the question.

Question 06.3: Beta Decay of Strontium-89

Determining Product Values for Beta Decay (2 Marks)

Context Equation: ⁸⁹₃₈Sr → ᴬ_Z Y + β

✅ Correct Answer

A = 89 [1 mark]

Z = 39 [1 mark]

*Note: Mark scheme requires values in this exact order.

📐 Step-by-Step Balancing

A beta particle is a fast-moving electron emitted from the nucleus: ⁰₋₁e or ⁰₋₁β.
Mass number (top): 89 = A + 0 → A = 89.
Atomic number (bottom): 38 = Z + (-1) → Z = 38 + 1 = 39.

💡 Key Knowledge

In beta decay, a neutron turns into a proton and an electron. The electron is emitted as a beta particle. Hence:

Mass number stays unchanged.
Atomic number increases by 1.

❌ Common Errors

Subtracting 1 from atomic number (writing Z = 37 instead of 39).
Swapping the values of A and Z around on the answer lines.

Question 06.4: Nature of Gamma Radiation

Identifying Radiation Type (1 Mark)

✅ Correct Answer

Electromagnetic waves [1 mark]

💡 Key Knowledge

Gamma radiation is high-frequency, high-energy electromagnetic waves.
It has no mass and no charge, so its emission does not change the mass or atomic number of the parent nucleus.

❌ Common Errors

Selecting "Particles with no charge" (confusing gamma rays with neutrons). Gamma rays are waves, not matter particles.

Question 06.5: Comparing Radiation Properties

Extended 6-Mark Comparison & Explanation

🧠 How to Get Level 3 (5–6 Marks)

The mark scheme states: "To access level 3 the answer should compare alpha, beta and gamma radiation and provide some explanation of their properties."

Identify properties: State what each consists of, penetrating power, range in air, and ionising ability.
Compare them: Use comparative words (e.g. "most ionising", "least penetrating", "longer range than...").
Explain: Explain why they behave this way (e.g. charge, mass, speed).

💡 Summary Table for Quick Recall

Property	Alpha (α)	Beta (β)	Gamma (γ)
Nature / Composition	Helium nucleus (2 protons, 2 neutrons)	Fast-moving electron (from nucleus)	Electromagnetic wave / photon
Charge & Mass	Charge +2, Mass 4	Charge -1, Negligible mass	No charge (0), No mass (0)
Penetrating Power	Least penetrating (stopped by paper or skin)	Moderately penetrating (stopped by ~5 mm aluminium)	Most penetrating (reduced by thick lead or thick concrete)
Range in Air	Shortest (a few cm, ~3–5 cm)	Moderate (up to ~1 metre)	Longest / Infinite (travels very large distances)
Ionising Power	Most ionising	Moderately ionising	Least ionising

✅ Model 6-Mark Answer Structure

1. Alpha Radiation: Consists of 2 protons and 2 neutrons (a helium nucleus) with a +2 charge. Because it has a large mass and charge, it is most ionising. Due to frequent ionising collisions, it loses energy rapidly, giving it the shortest range in air (a few cm) and the least penetrating power (stopped by paper or skin).

2. Beta Radiation: Consists of a high-speed electron with a -1 charge. It is moderately ionising (less than alpha, more than gamma). Consequently, it has a moderate range in air (~1 m) and is absorbed by a few millimetres of aluminium.

3. Gamma Radiation: An uncharged, high-frequency electromagnetic wave. Because it has no charge or mass, it interacts weakly with matter, making it the least ionising. As a result, it has the greatest penetrating power (only reduced by thick lead/concrete) and travels very large distances in air.

❌ Examiner Pitfalls & Common Mistakes

Confusing ionising and penetrating power: Students frequently mix these up. The more ionising radiation is (alpha), the less penetrating it is because it deposits its energy immediately!
Listing without comparing: Writing isolated sentences for each type without comparing them (e.g. saying "alpha goes 5 cm" without noting it is the shortest).
Missing explanations: Failing to link high ionisation to large charge (+2) or high penetration to zero charge/mass.
Saying gamma is "completely stopped": Gamma radiation is attenuated/reduced by lead, never 100% blocked.

Topics

Physics · P4: Atomic Structure

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Physics Paper 1 (Foundation), November 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.