AP Chemistry PES

Question

The link below is the picture that correlates with the question:

http://prntscr.com/hsqi56

 

Here's the question:

 

The above PES belongs to a neutral chlorine atom

 

(A) What wavelength of light would be required to eject a 3s electron from chlorine

(B) For the PES of a chloride ion, how would the following variables compare to the peaks on the PES above? Justify your answer

    (i) Number of peaks

    (ii) Height of the peaks

 

Answer 1

(A) It is generally accepted that BE (binding energy) is the energy to remove the electron and it is known that E_photon = hv where h is Planck's constant and v is the frequency of the light.  So, to answer part A, I think you need to know the frequency of the light being used and then substitute it and solve for E.  The PES shown is a bit unusual since it doesn't give the actual values of BE and I'm not sure what the numbers above each peak represent. They usually show the number of electrons, but since the first peak (lowest BE) has a value of 273 which should represent the 3p⁵ electrons is greater than the 3rd peak value of 20.2 which should be the 2p⁶ electrons, this interpretation doesn't make sense.  So, I don't think I can help with part A.

 

(B)  The chloride ion would have one additional electron in the 3p subshell. Thus

(i)  The number of peaks should be the same (5 peaks) because there are no additional subshells being occupied

(ii)  The height of the peaks should be the same except for the peak at the highest BE which should increase in height. This increase in height would be a result of the additional electron now occupying the 3p subshell.