1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Homework Question - Beta and Alpha decay

  1. Apr 5, 2014 #1
    Hi, i am new here. Thought it would be good to sign up as i have just started hitting the books in preparation for my AS Level exams. So this is my first question.

    I think i may have done this question correctly, but i was just seeing what other people think as i am not 100% sure about it.


    A nucleus of the radioactive isotope of bismuth Bi (213) and (83) emits a beta particle, then an alpha particle, then another beta particle before it becomes stable.

    a) Show that the stable nucleus formed is a Bismuth isotope

    My Attempt at it

    Bi (213) (83) → Bi (213) (84) I have added one to the proton number, because in beta decay, a neutron turns into a proton, so the nucleon number remains the same, but the proton number goes up by 1.

    Then for Alpha, it becomes Bi (209) (82). I have taken 4 from the nucleon number and 2 from the proton number because an alpha particle consists of 2 protons and 2 neutrons.

    Then after the second beta decay i ended up with Bi (209) (83).

    Is this correct?

    Thanks for your help.
  2. jcsd
  3. Apr 5, 2014 #2


    User Avatar
    Homework Helper

    Looks good, but I'm not sure whether they're expecting you to write step by step proper nuclear reactions (including the electrons and antineutrinos and the alpha particles ).
  4. Apr 5, 2014 #3


    User Avatar
    2017 Award

    Staff: Mentor

    I agree with the numbers, but the symbols of the intermediate nuclei are not "Bi".
  5. Apr 5, 2014 #4
    Thanks for the replies.

    Curious3141, i dont think you do have to, but i know how to if i were to be asked in an exam. Just write B (0) (-1) add the anti neutrino (the v with the line above it) to the beta decay, and fore alpha, write the alpha symbol with (4) (2).

    mfb, I just used "Bi" as that was the element quoted in the question. I know that the elements that are formed inbetween are not "Bi".

    Expect me to ask more questions later on, as i will be starting to revise Leptons and all of that stuff that im really weak with. :D
  6. Apr 5, 2014 #5


    User Avatar
    Homework Helper

    No, but mfb is right - in writing that way, it's wrong. It's OK to omit the symbol entirely (if you're just writing informally), but to actually put "Bi" there is wrong.
  7. Apr 5, 2014 #6
    The proton number?
  8. Apr 5, 2014 #7


    User Avatar
    Homework Helper

    Steamking's post (that you're replying to) has vanished. But you're correct. I prefer to refer to it as the atomic number, because that's a good reminder that this is the number that determines what atom it is.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted