1. E = hf E – energy of a quantum (Joules) h – Plank’s constant (6.626 x 10 -34 J  s) f – frequency of absorbed or emitted EMR

2. Wave-Particle Duality: The Beginnings of Quantum Mechanics

3. Describe the photoelectric effect. Understand the basics of wave-particle duality. Understand the difference between quantum, photon and electron. Be able to explain how the Bohr model fits with knowledge of line spectra.

4. PHOTOELECTRIC EFFECT Shining light on a metal surface will immediately eject electrons. Electrons given enough energy (ionization) can escape the attraction of the nucleus. *Light is acting like a “particle” in this experiment – collision.

5. Einstein (1905) - electromagnetic radiation is a stream of tiny bundles of energy called photons. Photons have no mass but carry a quantum of energy. One photon can remove one electron. Light is an electromagnetic wave, yet it contains particle-like photons of energy.

6. Only high frequency light (> 1.14 x 10 15 Hz) will eject electrons - acting as particle. Can only explain it if you think of it using photons in a collision.

7. Only more intense light (higher amplitude) will eject more electrons - acting as wave. Can only explain it if you think of it as changing the size of the wave.

8. Compton (1922) – first experiment to show particle and wave properties of EMR simultaneously. Incoming x-rays lost energy and scattered in a way that can be explained with physics of collisions.

9. Quantum Mechanical Model of the Atom

10. Helium nuclei – alpha (α) particles - fired at thin gold foil reflected strongly. Discovered the nucleus – electrons just fly around. Rutherford (1911) - “Gold foil ” experiment.

12. Bohr (1922) – explained unique line spectrums by restricting electrons to fixed orbits with different quantized energy levels.

13. 1.Electron absorbs radiation and jumps from ground state (its resting state) to a higher unstable energy level (excited state). 2.Electron soon loses energy and drops back down to a lower energy level – emitting the absorbed EMR.

14. Levels are discrete like quanta – no in between. Each jump/drop is associated with a specific frequency photon - same transition, same photon.

16. The size of nucleus will affect electron position around the atom. Cl: 17 e - Na: 11 p + 11 e - 17 p +

17. *Each element has a unique line spectrum as each element has a unique atomic configuration.

18. Absorption spectrum – portion of visible light absorbed by an element – heating up. Emission spectrum – portion of visible light emitted by that element – cooling down.

19. CAN YOU ? / HAVE YOU? Describe the photoelectric effect. Understand the basics of wave-particle duality. Understand the difference between quantum, photon and electron. Be able to explain how the Bohr model fits with knowledge of line spectra.