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Chemistry LibreTexts

19.E: Nuclear Chemistry



 Balance each of the following nuclear equations and indicate the type of nuclear reaction (\(\alpha\)-emission, \(\beta\)-emission, fission, fusion, or “other”).

  1. \(\mathrm{\ce{^{239}_{94}Pu}+\ce{^1_0n}\rightarrow \ce{^{130}_{50}Sn}+{?}+3^1_0n}\)
  2. \(\mathrm{{?} + \ce{^{6}_{3}Li} \rightarrow 2^4_2He}\)
  3. \(\mathrm{\ce{^{210}_{84}Po}\rightarrow \ce{^4_2He}}+{?}\)
  4. \(\mathrm{\ce{^{235}_{92}U}+{^1_0n}\rightarrow \ce{^{72}_{30}?}+{?}+4^1_0n}\)
  5. \(\mathrm{\ce{^{125}_{53}I}\rightarrow \ce{^{125}_{53}I}+{?}}\)
  6. \(\mathrm{\ce{^{238}_{92}U}\rightarrow {?}+\ce{^{234}_{?}Th}}\)
  7. \(\mathrm{\ce{^{235}_{92}U}+{^1_0n}\rightarrow \ce{^{86}_{?}Br}+\ce{^{147}_{?}?}+{?^1_0n}}\)
  8. \(\mathrm{\ce{^{234}_{90}Th}\rightarrow {?}+\ce{^{234}_{91}?}}\)


 The isotope \(\ce{^{137}_{55}Cs}\) undergoes beta emission with a half-life of 30 years.

  1. Write a balanced nuclear equation for this reaction.
  2. What fraction of \(\textrm{Cs-137}\) remains in a sample of the isotope after 60 years?
  3. What mass of \(\textrm{Cs}\) will be left in a 24.0 g sample of \(\ce{^{137}_{55}Cs}\) after 90 years?                                           
  4. What fraction of \(\textrm{Cs-137}\) has decayed after 120 years?


 What is the half-life of an isotope that is 75% decayed after 16 days?


Explain what makes an isotope radioactive. Why do radioactive isotopes undergo radioactive decay?  How does the energy released by nuclear reactions compare to that released by ordinary chemical reactions?  Why?


 Write balanced nuclear equations for:

  1. positron emission by \(\textrm{Sr-83}\)
  2. the fusion of two \(\textrm{C-12}\) nuclei to give another nucleus and a neutron.
  3. the fission of \(\textrm{U-235}\) to give \(\textrm{Ba-140}\), another nucleus and an excess of two neutrons.


 What new element is formed when \(\textrm{K-40}\) decays by \(\beta\)-emission?  Is the new element formed likely to be stable?  Why or why not?


 Why is nuclear fission considered a “chain reaction”?  What is “critical” about critical mass? Why does nuclear fission produce radioactive waste?