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## Main Question or Discussion Point

This should be easy but I'm totally stuck here.

So I'm calculating the K

The only thing I could think was that the error was due to the approximation of the screening constant. Solving the equation backwards for the "table value"of K-beta gives an Z

Could anybody tell me what I am missing here? I'm super thankful for all the help I can get.

So I'm calculating the K

_{β}line (emitted energy) of Molybdenum (Mo 42). I'm using Moseley's law and am moving from the M-shell to the K-shell. Recall Moseley's law is E = 13.6 eV (Z-σ)^{2}*1/n^{2}. The effective formula for the energy emitted is thus E = 13.6 eV (Z-σ)^{2}*(1- (⅓^{2}) since I am moving from n = 3 to n = 1. σ is the screening constant of n =3 of Molybdenum. Using a screening constant of 1 (I know this is incorrect, but bare with me) I get that the difference in energy is 20.321 keV. The answer according to all tables I've seen is 19.607 keV.The only thing I could think was that the error was due to the approximation of the screening constant. Solving the equation backwards for the "table value"of K-beta gives an Z

_{eff}of 40.27. I can't fit the screening constant into that equation, since it is 4.15, as calculated with Slater's rules.Could anybody tell me what I am missing here? I'm super thankful for all the help I can get.