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Homework Help: Completion of radioactivity equation

  1. Aug 25, 2011 #1
    1. The problem statement, all variables and given/known data

    Complete this reaction equation:
    [tex]^9_4 Be + ^1_0 n \rightarrow ^4_2 He + ?[/tex]

    2. Relevant equations

    Not relevant

    3. The attempt at a solution

    I find the answer to be [itex]^6_2 He[/itex] , but the answer key in my book says [itex]^7_3 Li[/itex]

    I can't see how that can be right, please help!
    Last edited: Aug 25, 2011
  2. jcsd
  3. Aug 25, 2011 #2


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    [tex]^9_4 be + ^1_0 n \rightarrow ^3_1 H + ?[/tex]

    If the first "product" was in fact Tritium, I could understand the Lithium, other wise your conjecture seems appropriate.
  4. Aug 25, 2011 #3
    Considering neutron absorption by Be-9 produces Be-10 which decays by beta to B-10, I think the book may be wrong.
  5. Aug 25, 2011 #4


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    I think everyone can agree that helium-6 does not exist as a possible end product.
  6. Aug 25, 2011 #5
    I know that's an impossible nuclide, (it won't exist) , but that only indicates my book must contain an error in that problem. Thanks for settling that matter ! :approve:

    Here's a similar one, which also gives me a somewhat strange answer:

    [tex]^{10}_4 Be + ^2_1 H \rightarrow X + ^{11}_6 C[/tex]

    The X must then be: [itex]^1_{-1} X[/itex]. :rofl: As far as I know this is not a common particle, but it might be here that the X stands for one neutron and one electron, that is [itex]^1_0 n + ^0_{-1} e[/itex].

    What do you think?
  7. Aug 25, 2011 #6
    It seems your book is skipping intermediate steps as well, since the reaction should produce boron-12, or more likely boron-11 which would be a fusion reaction releasing a neutron, which despite being stable, then beta decays to carbon-11, which is unstable.

    Methinks you might want to tell the professor that the reactions and decays in the book are not realistic.

    But, yes, that would have to be the result of that problem.
  8. Aug 25, 2011 #7


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    The typical reaction for neutron bombardment of beryllium is:

    Be-9 + neutron yields 2 He-4 + 2 neutrons

    meaning beryllium acts as a neutron multiplier.

    See: http://en.wikipedia.org/wiki/Beryllium
  9. Aug 26, 2011 #8
    Well, yes, maybe my book is written to oversimplify some things ... then the reactions and decays most probably can't become realistic. Maybe I should find a book describing the intermediate steps as well, which I can read beside the curriculum, so I'll know more often what these steps are like. Any suggestions for a good book on this topic? (I'm sitting in a library right now today, so I might be able to find it here)

    Many thanks for checking my answer !!!
  10. Aug 29, 2011 #9
    If you mean a book that shows the normal modes of decay and their end products, the Chart of Nuclides published by Knolls Aomic Power Lab (KAPL) is what I use.
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