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CAIE IGCSE Physics Radioactive Decay Question Bank

Practise describing spontaneous random decay, updating proton and nucleon numbers for alpha or beta emission and completing balanced nuclide equations.

Syllabus
2026–2028
Course
Physics 0625

Exam points

  • state that an individual unstable nucleus decays spontaneously and its decay time cannot be predicted
  • for alpha decay subtract 4 from A and 2 from Z, producing a helium nucleus
  • for beta-minus decay keep A constant and increase Z by 1 as a neutron becomes a proton and electron

Covered syllabus points

5.2.3.1—Radioactive decay is a change in an5.2.3.2—During α-decay or β-decay, the nucleus5.2.3.3—Isotopes of an element may be5.2.3.4—Effect of α-decay, β-decay and5.2.3.5—Decay equations, using nuclide

5.2.3 Radioactive decay question 1

[Maximum number: 2]

Fig. 11.2 shows a geologist holding a radiation detector near a rock.

Fig. 11.2

Fig. 11.2

She holds the detector in a fixed position and records the readings shown in Table 11.1.

Table 11.1

Table 11.1

Explain the changes in the detector readings.

5.2.3 Radioactive decay question 2

[Maximum number: 1]

Which statement about alpha decay is correct?

A

The nucleus loses electrons.

B

The nucleus changes to that of a different element.

C

The nucleus does not decay until after one half-life.

D

After two half-lives, alpha decay always stops.

5.2.3 Radioactive decay question 3

[Maximum number: 4]

Strontium-90 (3890Sr)\left({ }_{38}^{90} \mathrm{Sr}\right) is a radioactive isotope that contains 38 protons and 52 neutrons. Strontium-90 decays to form an isotope of yttrium (Y) by emitting beta ( β\beta ) particles.

Question (a)

(a)

Suggest how the nucleus of a stable isotope of strontium differs from a nucleus of strontium-90. Explain your answer.
suggestion
explanation

[ 2 ]

Question (b)

(b)

Complete the nuclide equation for the decay of strontium-90 to yttrium.

3890Sr⟶………⋯…⋯Y+………⋯…⋯β{ }_{38}^{90} \mathrm{Sr} \longrightarrow{ }_{\ldots \ldots \ldots}^{\cdots \ldots \cdots} \mathrm{Y}+{ }_{\ldots \ldots \ldots}^{\cdots \ldots \cdots} \beta
[ 2 ]
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