AQA AS Level Physics Paper 2, June 2023: Question 22

1 mark · Medium difficulty · Multiple Choice

Determine the nucleon number and proton number of nuclide X formed after bismuth-209 absorbs a neutron and subsequently decays by emitting a beta-minus particle and an alpha particle.

Practise this question

Question

Multiple-choice question 22. A nucleus of bismuth-209 (Bi-209 with nucleon number 209 and proton number 83) absorbs a neutron and decays in two stages via one beta-minus particle and one alpha particle emission to form nuclide X. A table lists four options (A, B, C, D) with corresponding nucleon numbers and proton numbers for X.
Question text

22 A nucleus of bismuth-209 Bi absorbs a neutron. The newly formed nucleus

subsequently decays in two stages to form a nucleus of nuclide X.

One beta-minus particle and one alpha particle are emitted during these two decays.

What are the nucleon number and the proton number of X?

[1 mark]

Nucleon number Proton number

A 205 82

B 205 83

C 206 82

D 206 83

Mark scheme

Show the mark scheme Mark scheme showing question number 22 with the correct answer option C, corresponding to a nucleon number of 206 and a proton number of 82.

22 C 206 82

How to answer it

Overall Difficulty: Medium

Radioactive Decay and Nucleon Transformations

What this question tests

This question assesses your understanding of nuclear equations, conservation laws in radioactive decay (specifically nucleon number and proton number conservation), and the structural changes caused by neutron absorption, beta-minus emission, and alpha emission.

Question 2.2

Bismuth-209 Decay Chain Analysis

✅ Correct Answer

Option C

Nucleon number: 206
Proton number: 82

1 mark awarded for selecting option C.

💡 Key Knowledge

  • Neutron absorption: Adds 1 to the nucleon number and 0 to the proton number.
  • Alpha particle emission (He-4): Decreases nucleon number by 4 and proton number by 2.
  • Beta-minus emission (e-0): Leaves nucleon number unchanged and increases proton number by 1.

🧠 Exam Technique

Do this step-by-step by writing out mini nuclear equations for each stage. Track the top numbers (nucleons) and bottom numbers (protons) separately to avoid arithmetic slips under exam pressure.

❌ Common Errors

  • Forgetting that absorbing a neutron changes the initial starting nuclide before any decays occur.
  • Subtractive errors with beta-minus decay (mistakenly decreasing the proton number instead of increasing it).

📐 Step-by-Step Breakdown

  1. Initial nucleus: Bismuth-209 has nucleon number 209 and proton number 83 . Written as 20983Bi.
  2. Neutron absorption: Adds a neutron (10n).
    New nucleon number = 209 + 1 = 210
    New proton number = 83 + 0 = 83
    Nuclide becomes 21083Bi.
  3. Alpha emission: Emits an alpha particle (42He).
    Nucleon number = 210 - 4 = 206
    Proton number = 83 - 2 = 81
  4. Beta-minus emission: Emits a beta-minus particle (0-1e).
    Nucleon number = 206 - 0 = 206
    Proton number = 81 - (-1) = 81 + 1 = 82
  5. Final Nuclide X: Nucleon number 206 , Proton number 82 , which matches option C.

Topics

Physics · 3.2 Particles and radiation

Question and mark scheme from the AQA AS Level Physics examination, Paper 2, June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.