Photoelectron Spectroscopy Worksheet
http://www.scribd.com/doc/91590491/9/Photoelectron-Spectroscopy
1.
In a photoelectron spectrum, photons of 165.7 MJ/mol strike atoms of an
unknown element. If the kinetic energy of the ejected electrons is
25.4 MJ/mol, what is the ionization energy of the element?
165.7 MJ/mol – 25.4 MJ/mol = 140.3 MJ/mol
2.
What determines the position and the height (intensity) of each peak in a
photoelectron spectrum?
The position of each peak is identified by the ionization energy, the height of
each peak identifies the ratio of electrons in each level or orbital.
3.
Why is the distance of the energy level from the nucleus important in
determining the corresponding peak position in the photoelectron spectrum?
The closer the electron, the more interaction and attraction, the more energy
is needed to get rid of that electron.
4.
The ionization energy of an electron from the first energy level of lithium is
6.26 MJ/mol. The ionization energy of an electron for the second energy
level of lithium is 0.52 MJ/mol.
a)
Draw an energy level diagram for lithium.
2s1
1s2
b)
Sketch the photoelectron spectrum for lithium; include the values of the
ionization energies stated above.
5.
Based on the information provided below, draw a photoelectron spectrum
for argon. Indicate the relative intensities and positions of all peaks.
1s2
- 309.0
6.
2s2
- 31.5
2p6
- 24.1
3s2
- 2.83
3p6
- 1.52
Identify the element in the photoelectron spectrum shown below. Explain
your reasoning.
1s2
2s2
2p6
3s2
Mg
7.
Identify if either of the following statements is correct. If yes, why. If not,
why not:
a)
The photoelectron spectrum of Mg 2+ is expected to be identical to the
photoelectron spectrum of Ne.
Since these 2 species are isoelectronic, same number of electrons, it
would initially lead one to believe they would be the same. However, Mg
has 12 protons, whereas Ne has 10, therefore there is a different level of
interaction between the nucleus and the electrons.
The photoelectron spectrum would be different.
b)
The photoelectron spectrum of 35Cl is identical to the photoelectron
spectrum of 37Cl.
The photoelectron spectrum would be the same since the Zeff and
number of electrons is the same.
8.
Is it possible to deduce the electron configuration for an atom from its
photoelectron spectrum? If so, explain how. If not, explain why not.
Yes. By looking at the relative height of the peaks the number of electrons
at that level could be identified, and by identifying the energy involved it
stripping electrons from the atom which level the electrons are in could be
identified.
Simulated Photoelectron Spectrum of Potassium.
9.
Why is the peak at 0.42 MJ/mol in the K photoelectron spectrum identified
as being in the 4th energy level?
Since there are 6 peaks, with the peak at 347 identifying 1s2 electrons, then
each succeeding peak must be the next closest orbital.
1s2
2s2
2p6
3s2
3p6
4s1