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Homework Help: Isotopes, atomic mass, abundance

  1. Jun 8, 2016 #1
    1. The problem statement, all variables and given/known data
    Suppose the element A contains three isotopes, 86A (atomic mass 85.909 u, abundance 16.19%) 87A (atomic mass 86.908, abundance 7.00%) and 88A (atomic mass 87.906 u). What would be the atomic mass of A that would appear in the periodic table?

    2. Relevant equations
    (A1 x %A1) + (A2 x %A2) + (A3 x (1-(%1 +%2)) = answer

    3. The attempt at a solution

    16.19% + 7.00% = 23.19%

    100% - 23.19% = 76.81% --> so that would be the 88A abundance % right?

    then I'm confused from there. Please help
  2. jcsd
  3. Jun 8, 2016 #2


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    2017 Award

    Staff: Mentor

    Just plug everything into the equation you have.
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