1. Evidence of Energy Levels

2. e-e- e-e- Ground state Excited state Electrons can only be at specific energy levels, NOT between levels.

3. Energy Level Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 329 A B CD Ground state Energy Four excited states

4. Color = Energy of Photons Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 329

5. Spectroscopy The science of analyzing matter using electromagnetic emission or absorption spectra. Used in many fields of science such as astronomy or forensics.

6. Atomic Emission Spectrum A characteristic set of colored lines that is unique for each element (“fingerprint”) –Different # of electrons Caused by the electrons releasing energy as they go from the excited state back down to the ground state –Each line corresponds to a specific photon of light being emitted

7. Excited vs. Ground State Ground State: the lowest possible energy of an atom described by quantum mechanics Excited State: electrons jump to higher energy levels due to an input of energy –It takes a quantum of energy to jump electron to the next higher energy level –Quantum = amt. of energy needed to move an e - from one energy level to the next

8. #7 When energy is added to an atom, it causes the electrons to jump up to higher energy levels (become “excited”). They release energy when they return to the ground state.

9. An Excited Lithium Atom Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 326 Photon of red light emitted Li atom in lower energy state Excited Li atom Energy

10. An Excited Lithium Atom Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 326 Photon of red light emitted Li atom in lower energy state Excited Li atom Energy

11. Excitation of Hydrogen Atoms Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 328

12. Return to Ground State

13. Frequency A Frequency B Frequency C n = 2 n = 1 n = 3

14. Frequency A Frequency B Frequency C n = 2 n = 1 n = 3 A B C A + B = C