2. PES  Provides explanation for shells and orbitals in quantum theory  Photoelectric effect —  Utilization of photons to remove electrons from atoms  Photons have been energized, analyzing the energy needed to remove electrons from an atom/compound  Photoelectric spectrum —  Energy on x-axis  Number of electrons in a subshell on y axis

3. Photoelectric SpectrumPhotoelectric Spectrum  Peaks —  Number of subshells/orbitals  Peak heights —  Number of electrons in subshell  Electrons within the same subshell have similar energy values but different orbital energies, energy values vary among subshells  Shells with high energies indicate electrons located close to nucleus

5. Example 1: NaExample 1: Na

6. Example 2:Example 2:  A third period element in the periodic table forms a PES spectrum with three peaks, in the ratio 2:2:1. Name this element. A)Aluminum B)Boron C)Carbon D)Sodium

7. Example 3:Example 3:  Aluminum has the following electron configuration: 1s 2 2s 2 2p 6 3s 2 3p 1 A)How many peaks should be expected in a PES spectrum for Al? B)Which electrons will show the highest energies? Why?

8. Example 3: (cont.)Example 3: (cont.)  Aluminum has the following electron configuration: 1s 2 2s 2 2p 6 3s 2 3p 1 C) Which peak on the spectrum will be the most intense/largest? Why? D) Explain why the peaks for the 3s and 3p electrons would be closely grouped and why they are different than electrons in the 2s and 2p orbitals.