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Homework Help: From Uranium isotope to thorium isotope

  1. Sep 15, 2012 #1
    I need to complete the following sentence. If I think that electron capture or alpha decay does not occur in my decay process, I have to type a '0' (zero) in the appropriate box:

    Converting an atom of the isotope Uranium (238-92) into an atom of thorium can be accomplished if an electron capture process occurs___times and an alpha decay occurs ___times. The resulting isotope has a mass number___ and an atomic number___ .

    Initially I thought the right answers were: zero, one, 234, 90. But after I realized that I cannot say one times because times is plural. Is it only one right answer of there are different options? The resulting isotope has definitely a atomic number of 90, but I am not sure about the rest. Thanks for your help
  2. jcsd
  3. Sep 16, 2012 #2
    Your answers are quite correct. There is no other answer because there is no allowance for a beta decay, and electron capture processes would usually only happen with a proton-rich isotope (mass number lower than those of the most stable or abundant isotopes of the element).

    If beta decays were allowed for, then "beta (-) decay occurs 2 times and alpha decay occurs 2 times ... 90 ... 230 ..." might be an alternative answer, but the question is simply not worded that way.

    I think you should ignore the slightly ungrammatical "1 times" in a question like this.
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