This question is about the use of radioactivity in veterinary medicine to treat localised disease.
A cat has a small skin tumour on its flank, which is about 3 millimetres deep. A vet treats the tumour using radiation therapy by injecting a radioactive isotope called yttrium-90 into the tumour. Yttrium-90 decays by emitting beta-minus (β−\beta^-β−) particles.
Yttrium-90 is written using this symbol:
3990Y ^{90}_{39}\text{Y} 3990YHow many protons does a nucleus of yttrium-90 contain?
How many neutrons does a nucleus of yttrium-90 contain?
Yttrium-89 is a different stable isotope of yttrium. What are isotopes?
When yttrium-90 decays, a beta-minus particle is emitted and it changes into zirconium (Zr\text{Zr}Zr). Complete the nuclear equation by finding the missing mass number AAA and atomic number ZZZ for the zirconium nucleus:
3990Y→ ZAZr+−10β− ^{90}_{39}\text{Y} \rightarrow \ ^{A}_{Z}\text{Zr} + ^{0}_{-1}\beta^{-} 3990Y→ ZAZr+−10β−The tumour is about 3 millimetres deep. Explain why beta radiation is more suitable than alpha or gamma radiations for this treatment.
The energy from the beta radiation is expected to destroy the cells in the tumour over a treatment period of several days.
The most suitable half-life for the radioactive source would be:
Explain your choice.
