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Homework Help: Ionizing an electron with light

  1. Mar 26, 2012 #1
    What wavelength of light ,λ, would be necessary to ionize an electron at n = 2 in a hydrogen atom?

    In my notes there are two equations that seem relevant to my question they are:

    E=hc/λ and -2.18 x 10-18 J((Z^2/n final^2)-(Z^2/n initial^2))

    where h is planks constant, c is the speed of light, Z is the atomic number of the element, in my case hydrogen, and n is the state the electron is in. I think it means energy state.

    I tried to think of something, but I don't know. What does it mean by ionizing an electron??
  2. jcsd
  3. Mar 27, 2012 #2


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    It should have been worded "ionizing a hydrogen atom", as ionization is defined as the removal of an electron from an atom or molecule. So your question asks you to calculate how much energy does it take to completely remove an electron from hydrogen that has its electron already excited to the n=2 orbital and then convert that energy into a wavelength of light.
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