1. 6.1.2 Energy Levels Photons in / Photons out

2. Ionization IONIZATION ENERGIES Energy needed to liberate electron from that level. GROUND STATE Lowest possible energy state for an electron in an atom.

3. A photon strikes an electron in the ground state of a hydrogen atom, liberating the electron. –What minimum energy did this photon have? Example #1 13.6 eV

4. A photon strikes an electron in the ground state of a hydrogen atom, liberating the electron. –What is the frequency of the photon that could provide this energy? Example #1 2.176 x 10 -18 J

5. A photon strikes an electron in the ground state of a hydrogen atom, liberating the electron. –What is the frequency of the photon that could provide this energy? Example #1 E photon = hf 2.176 x 10 -18 J = (6.63 x 10 -34 J·s) f f = 3.3 x 10 15 Hz

6. What happens to an electron in the n = 2 state of a hydrogen atom if it is hit by a 5.4 electron- volt photon? Example #2 The electron will leave the atom with a kinetic energy of 2.0 eV.

7. Level Jumps An electron will jump to a higher level if the ABSORBED photon has exactly the right energy. When an electron drops to a lower level a photon is EMITTED Equation

8. What energy is needed to move an electron from the ground state of a hydrogen atom to its n = 4 level? Example #3 E photon = E i – E f E photon = - 13.6 eV – - 0.85 eV E photon = - 12.75 eV

9. An electron drops from the n = 4 level to the n = 3 level of a hydrogen atom. –What is the energy of the emitted photon? Example #4 E photon = E i – E f E photon = - 0.85 eV – - 1.51 eV E photon = + 0.66 eV

10. An electron drops from the n = 4 level to the n = 3 level of a hydrogen atom. –What is the frequency of this photon? Example #4 E photon = hf 1.056 x 10 -19 J = (6.63 x 10 -34 J·s) f f =1.6 x 10 14 Hz

11. When electrons drop from one energy level to another they can follow any path to the lower state. Each downward step produces a photon with a different energy. –How many different photons could be produced in a transition from the n = 4 level of hydrogen to the n = 1 level? –How many different photons could be produced in a transition from the d-level to the b-level of a mercury atom? Example #5 6 possible photons dcbdcb 3 possible photons n =4 n = 3 n = 2 n = 1

12. Absorption/Emission Spectrum An EMISSION SPECTRUM is a pattern of bright lines on a dark background. –Analyze glow of a heated sample An ABSORPTION SPECTRUM is a pattern of dark bands on a continuous spectrum. –Pass white light through a cold sample.

13. Absorption/Emission Spectrum The existence of spectrums demonstrates that: –Energy in atoms is QUANATIZED – comes in discrete jumps. –Atoms can produce only specific sets of PHOTONS.

14. End of 6.1.2