Strontium-90 ($^{90}_{38}\text{Sr}$) refers to a radioactive isotope of strontium.
(a(i))[1]
Explain the meaning of isotopes.
(a(ii))[2]
Complete Table 9.1 on strontium-90.
(b(i))[2]
Suggest why strontium-90 is a suitable radioactive source for measuring the thickness of the metal sheets.
(b(ii))[2]
The strontium-90 source is exchanged for a new source after $15\,\text{years}$. Using Fig. 9.1, suggest why a strontium-90 source older than $15\,\text{years}$ has to be replaced by a new source.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Atoms of the same element with the same number of protons but different numbers of neutrons” …