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Homework Help: Bhor for He atom

  1. Apr 8, 2005 #1
    A singly ionized helium atom (He+) has only one electron in orbit about the nucleus. What is the radius of the ion when it is in Bohr orbit number 3.0?

    I used r=n^2*ao, but this equation looks like its only for hydrogen atoms. I'm just a bit confused because my books seemed to give the same rules for He and Li atoms.
  2. jcsd
  3. Apr 8, 2005 #2


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    a0 is different for the He+-ion (or the Li++-ion) than that for the H-atom. When deriving a0, make the nuclear charge z=2 (instead of z=1). That's the only change you need to make, and you will be good.
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