CAIE IGCSE Physics Neutron Excess and Nuclear Instability

Practise comparing stable and radioactive isotopes by neutron content and explain instability through an excess of neutrons or a nucleus that is too heavy.

Exam points

compare isotopes of one element and identify the unstable nucleus as having excess neutrons
explain that a nucleus may be radioactive because it contains too many neutrons or is too heavy

[Maximum number: 2]

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

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

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5.2.3.3—Isotopes of an element may be question 1