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

2. Explain the basics of wave-particle duality.
Define the relationship between quantum, photon and electron.
Describe how a produced line spectra relates to the Bohr diagram for a specific element.
Additional KEY Terms
Absorption Spectra Threshold energy

3. PHOTOELECTRIC EFFECT
Under certain conditions, shining light on a metal surface will eject electrons.
Electrons given enough energy (threshold energy) can escape the attraction of the nucleus.
*Light is acting like a “particle” in this experiment – collision.

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

5. 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.

6. Photons have no mass but carry a quantum of energy.
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.

7. 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. Bohr (1922) – restricting electrons to fixed orbits (n) with different quantized energy levels.
Created a math equation for energy of each orbit.
Equations correctly predicted the
line colours of hydrogen spectra.
Energyn = -(2.18 x J)/n2

11. Electron absorbs radiation and jumps from
ground state (its resting state) to a higher unstable energy level (excited state).
Electron soon loses energy and drops back down to a lower energy level – emitting the absorbed EMR.
Absorption
Ionization
Free Atom e−
EMR
EMR e−
Excited State e−
Ground State
nucleus
> Threshold Energy
< Threshold Energy

12. ΔE = E higher-energy orbit - E lower-energy orbit
= Ephoton emitted
= hf

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

14. The size of nucleus will affect electron position around the atom – and the size of “jump” energy.

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

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

17. CAN YOU / HAVE YOU?
Explain the basics of wave-particle duality.
Define the relationship between quantum, photon and electron.
Describe how a produced line spectra relates to the Bohr diagram for a specific element.
Additional KEY Terms
Absorption Spectra Threshold energy