(a)[2]
Explain what the term binding energy of a nucleus means.
(b)
The nuclear reaction below occurs: $^{235}_{92}\text{U} + ^{1}_{0}\text{n} \rightarrow ^{144}_{55}\text{Cs} + ^{90}_{x}\text{Rb} + y\,^{1}_{0}\text{n}$.
(b(i))[1]
Determine the values of $x$ and $y$ in this reaction.
(b(ii))[1]
State the name given to this type of nuclear reaction.
(b(iii))[1]
Compare the binding energy per nucleon of uranium-235 with that of caesium-144.
(c)[3]
Yttrium-90 decays to zirconium-90, which is stable. The sample begins as pure yttrium-90. Calculate the time, in days, at which the ratio of the number of yttrium-90 nuclei to the number of zirconium-90 nuclei is $2.0$. The half-life of yttrium-90 is $2.7\,\text{days}$.