DP Physics (first assessment 2025)

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Question 22N.1A.SL.TZ0.22

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Date November 2022 Marks available [Maximum mark: 1] Reference code 22N.1A.SL.TZ0.22
Level SL Paper 1A Time zone TZ0
Command term Question number 22 Adapted from N/A
22.
[Maximum mark: 1]
22N.1A.SL.TZ0.22

The nuclide uranium-237 follows a sequence of three decays to produce the nuclide uranium-233.

What is a possible sequence for these decays?


A.  Beta plus, alpha, beta plus

B.  Beta minus, alpha, beta minus

C.  Alpha, beta plus, beta minus

D.  Alpha, beta minus, beta plus

[1]

Markscheme

B

Examiners report

Another relatively challenging question, with less than 50% correct choices and the distribution of answers suggesting a lot of guesswork. An easy way to obtain the correct sequence of decays is by considering the proton number only, which after three decays returns to the original value because the initial and final nuclides are of the same chemical element. Alpha decay decreases the proton number by 2 while beta minus decay increases it by one, therefore two beta minus decays are required to compensate for the decrease in the proton number caused by the alpha decay.

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