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Photoelectron Spectroscopy: Exploring Atomic Structure and Ionization Energy, Study notes of Chemistry

Universiteit Antwerpen Management SchoolChemistry

What does a photoelectron spectrum tell us about the structure of an atom? ... POGIL™ Activities for AP* Chemistry ... Justify your answer.

Typology: Study notes

2021/2022

Uploaded on 08/05/2022

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Photoelectron Spectroscopy 1
Photoelectron Spectroscopy
What does a photoelectron spectrum tell us about the structure of an atom?
Why?
When scientists first discovered X-rays, they realized they could do more than just make images of people’s
bones. X-rays could also allow them to “see” inside the atom. They could not do this directly, but in look-
ing for patterns in ionization energy data they were able to determine the energy levels and sublevels of
electrons and how many electrons were in each level.
Model 1 – A Soccer Player in a Ditch
1. Consider Model 1. Imagine that a soccer player is trying to kick a ball out of a ditch.
a. What force of attraction is keeping the soccer ball at the bottom of the ditch?
b. Which type of energy must be overcome to get the ball out of the ditch—potential or kinetic?
c. Which type of energy must the ball have to get out of the ditch—potential or kinetic?
2. How much energy must be given to the ball by kicking it to get it out of the ditch?
3. Describe what happens to the ball if the soccer player’s kick provides:
a. 30 J of energy to the soccer ball in the ditch.
b. 45 J of energy to the soccer ball in the ditch.
c. 60 J of energy to the soccer ball in the ditch.
45 J = energy
needed to release the
ball from the ditch
pf3
pf4
pf5
pf8
pf9

Partial preview of the text

Download Photoelectron Spectroscopy: Exploring Atomic Structure and Ionization Energy and more Study notes Chemistry in PDF only on Docsity!

Photoelectron Spectroscopy 1

Photoelectron Spectroscopy

What does a photoelectron spectrum tell us about the structure of an atom?

Why?

When scientists first discovered X-rays, they realized they could do more than just make images of people’s bones. X-rays could also allow them to “see” inside the atom. They could not do this directly, but in look- ing for patterns in ionization energy data they were able to determine the energy levels and sublevels of electrons and how many electrons were in each level.

Model 1 – A Soccer Player in a Ditch

  1. Consider Model 1. Imagine that a soccer player is trying to kick a ball out of a ditch. a. What force of attraction is keeping the soccer ball at the bottom of the ditch? b. Which type of energy must be overcome to get the ball out of the ditch—potential or kinetic? c. Which type of energy must the ball have to get out of the ditch—potential or kinetic?
  2. How much energy must be given to the ball by kicking it to get it out of the ditch?
  3. Describe what happens to the ball if the soccer player’s kick provides: a. 30 J of energy to the soccer ball in the ditch. b. 45 J of energy to the soccer ball in the ditch. c. 60 J of energy to the soccer ball in the ditch. 45 J = energy needed to release the ball from the ditch

2 POGIL™^ Activities for AP* Chemistry

  1. For each of the scenarios in Question 3 where the ball successfully leaves the ditch, determine the kinetic energy the ball will have when it reaches the top of the ditch.
  2. Construct an algebraic equation that shows the relationship among the energy of the player’s kick (KEkick), the potential energy of gravity on the ball (PE) and the kinetic energy the ball will have as it leaves the ditch (KEroll).

Model 2 – A Hydrogen Atom

  1. Refer to Model 2. a. What force of attraction holds the electron in the hydrogen atom? b. Which type of energy needs to be overcome to remove an electron from the atom—potential or kinetic? c. What is supplying the energy to remove the electron from the atom in Model 2?
  2. Fill in the table below to show how the hydrogen atom (Model 2) parallels the ball in the ditch analogy (Model 1). Soccer Ball in the Ditch Hydrogen Atom Gravity Ball Player’s kick proton (^) electron photon

4 POGIL™^ Activities for AP* Chemistry

  1. If the kinetic energy of the photon is exactly equal to the ionization energy, the kinetic energy of the photoelectron should be zero. Verify that your equation is consistent with this idea. If not, revise your equation.
  2. Consider the equation you wrote in Question 12. What pieces of data do you need to know to calculate the ionization energy of a given electron?
  3. A photoelectron experiment is performed on a sample of silicon using photons with an energy of 1.43 × 105 kJ/mole. Photoelectrons are generated that have a kinetic energy of 1.34 × 105 kJ/mole. What was the ionization energy of these electrons?
  4. In the previous question, was only one atom of silicon involved, or were many atoms involved? What evidence do you have from the question to support your answer?

Model 3 – Multiple Energy Levels

  1. In the ditch diagram in Model 3, which player (A or B) will need to put more energy into their soccer ball to get it out of the ditch? Explain your answer in terms of both depth and potential energy.
  2. Consider the electrons in an atom of lithium as diagrammed in Model 3. Which electron, 1 or 3, will require more energy to be removed? Support your answer by discussing the attractive forces in the atom and how they might be different for electrons 1 and 3. 45 J A 30 J B Soccer Balls in a Ditch Lithium Atom 1 3 2 nucleus

Photoelectron Spectroscopy 5

  1. Compare electrons 1, 2 and 3 in terms of their ionization energy. Explain your reasoning.
  2. If a large number of lithium atoms are ionized in a PES experiment, each losing one randomly chosen electron, which ionization energy will be recorded more often, the lower IE or the higher IE? Justify your answer.

Model 4 – Photoelectron Spectra of Lithium

  1. Refer to the graph in Model 4. a. What are the units of the x -axis? b. What is unusual about the way the x -axis values are graphed? c. Which of the peaks in the graph represents electrons that are more tightly held by the nucleus? Explain your reasoning.
  2. How many atoms of lithium were ionized (theoretically) in order to obtain the data for the spec- trum above?
  3. Based on the energy values of the peaks, label each peak with the electrons in a lithium atom (see Model 3) to which they correspond. Photoelectron Intensity Ionization Energy (kJ/mole) 10000 8000 6000 4000 2000 0

Photoelectron Spectroscopy 7

  1. Look back at Model 4. Using the lithium PES spectrum as a starting point, show how the spectrum of the next larger element (beryllium) might be different. (Recall that Be will have one more proton in its nucleus and one more electron in its sublevels.)

Model 5 – Sulfur and Phosphorus

Photoelectron Intensity Ionization Energy (kJ/mole) 10000 8000 6000 4000 2000 0 Photoelectron Intensity Ionization Energy (kJ/mole) 300.0 200.0 100.0 30.0 20.0 10.0 2.0 1. A B C D E Phosphorus Photoelectron Intensity Ionization Energy (kJ/mole) 300.0 200.0 100.0 30.0 20.0 10.0 2.0 1. A B C D E Sulfur

8 POGIL™^ Activities for AP* Chemistry

  1. Refer to Model 5. a. The atomic structure of which atoms are represented by the PES spectra shown? b. List the number of protons and electrons in each atom. c. Draw a shell model for each atom based on the PES spectrums below. Label each shell in your models with the corresponding PES peak from Model 5.
  2. Consider the attractive and repulsive forces in the atoms of sulfur and phosphorus. a. Explain why most of the peaks in the sulfur spectrum are shifted to the left relative to the peaks in the phosphorus spectrum. b. Explain why peak E in the sulfur spectrum is shifted slightly right compared to peak E in the phosphorus spectrum.
  3. Sketch the PES spectrum for chlorine using the spectra in Model 5 as a guide.