1. Physics
Wave particle Duality
Models of the Atom

2. Waves Have a Particle Nature
Light can behave as particles of energy that possess kinetic energy and momentum
We see this when light strikes the surface of something – it transfers energy and momentum!
This was observed earlier in the century that when light above a minimum frequency value strikes the surface of specific metals, electrons are emitted from the metals
This is called the photoelectric effect – CLICK HERE view demo and do worksheet

3. Models of the Atom Major Contributors:
Thomson (Lord Kelvin)  early 1900’s
Rutherford  1920’s
Neils Bohr  2 years later!
Erwin Schrödinger - The Cloud Model

4. Bohr Model of the Hydrogen Atom
Bohr proposed that electrons hold their positions and DO NOT spiral towards the nucleus
Proposes (4) assumptions

5. Bohr’s Model Bohr’s (4) assumptions All forms of energy are quantized
The electron in a hydrogen atom can occupy only certain specific orbits of fixed radius and no others
An electron can jump to a higher orbit by absorbing a quantum of energy in the form of a photon
Each allowed orbit corresponds to a specific amount of energy - orbit closest to nucleus is the lowest

6. Hydrogen Atom
Click for demo P

7. Emission (Bright-Line) Spectra
When these frequencies are viewed in a spectroscope, the frequencies appear as a series of bright-lines against a dark background
These are called Bright-Line Spectrum or Emission Spectrum

8. Absorption-Spectra
Results from the absorption of photons and the promotion to higher energy levels
Occurs when a photon with the exact correct wavelength and frequency, thus energy, is absorbed
Shows up as a series of dark lines, resulting from the selective absorption of particular frequencies in the white-light spectrum

9. Practice probs A

10. When a Photon is released, we may see it!
1) n=6 = n=5
2) n=6 = n=4
3) n=6 = n=3
4) n=3 = n=1
5) n=2 = n=1

11. Practice probs 3

12. Energy of a Photon

13. Practice Probs
-3.4 eV

14. Practice Probs
8.82 eV

15. Practice Probs A

16. The Cloud Model
Click above for Demo

17. Practice Prob A