[填空题]
1.Uranium-235 $(^{235}_{92}U)$ has a nuclear mass of 235.044 u.
(1)State what is meant by mass defect.
(2)Calculate the mass defect of uranium-235. $δ$ = $u$
2.(1)Calculate the binding energy per nucleon of uranium-235. $binding energy per nucleon$ = $MeV$
(2)On the axes given, sketch the variation of the binding energy per nucleon with the nucleon number. Label the position of uranium-235. There is no need to add numbers to the axes.
3.Uranium-235 ( $^{235}_{92}U$) decays into thorium-231 ( $^{231}_{90}Th$).
Determine which nuclide has a higher binding energy per nucleon. Use the graph to justify your answer.
