State the definition of the binding energy of a nucleus.
A uranium-235 nucleus absorbs a neutron and becomes unstable. It then undergoes fission. One possible reaction is $^{235}_{92}\text{U} + ^{1}_{0}\text{n} \rightarrow ^{142}_{54}\text{Xe} + ^{90}_{38}\text{Sr} + \text{neutrons}$. Determine how many neutrons are produced in this fission reaction.
Table 8.1 gives the binding energies per nucleon for this fission reaction. Calculate the energy released, in MeV, when one nucleus of uranium-235 undergoes fission.
The isotope xenon-142 is unstable. The isotope xenon-132 is stable. Suggest why xenon-142 is unstable.
Xenon-142 decays into the isotope caesium-142. A sample initially contains only nuclei of xenon-142. After $6.0\,\text{s}$, the ratio $\frac{\text{number of decayed nuclei of xenon-142}}{\text{number of undecayed nuclei of xenon-142}}$ is $31$. Calculate the half-life of xenon-142. Show your working.