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Homework Help: Computing energy in the electron of Li 2+?

  1. Sep 12, 2013 #1
    1. The problem statement, all variables and given/known data
    Using the Bohr model of the atom, compute the energy in eV of the one electron in Li2+.

    2. Relevant equations

    [itex]E_n=\frac{m\cdot e^4 \cdot z^2}{2n^2 \cdot \hbar^2}[/itex]
    Where m= mass of electron, z= atomic number, e= charge of an electron, n is the energy level.

    ^ I think those are the right meanings of the variables...

    3. The attempt at a solution

    plugging in 1 for n, 3 for z, 9.11*10^-31 kg for m, -1.602*10^-19 Coulombs for e, and 1.054572×10^-34 J*s for h, we get
    E_1= ((9.11*10^-31 kg))*((-1.602*10^-19 C)^4)*(3^2)/(2(1.054572×10^-34 J s)^2) = 2.428×10^-37 s^6A^4/(kg m^4) (second to the 6 amperes to the fourth per kilogram meter to the fourth).

    This clearly doesn't seem right. What am I doing wrong? I need help...
  2. jcsd
  3. Sep 13, 2013 #2


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    Homework Helper

    Check the equation for the energy. ε02 is missing from the denominator.

    [itex]E_n=\frac{m\cdot e^4 \cdot z^2}{2n^2 \cdot \hbar^2\cdot ε_0^2}[/itex]

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