1. Electromagnetic Radiation
February 26, 2007
Chem 102B

2. Hydrogen Emission Spectrum
High-energy sparks inside a tube containing hydrogen gas (H2) cause the H-H bond to break, leaving atomic hydrogen.
The atomic hydrogen is excited, and when it relaxes it releases energy in the form of light.

3. Electromagnetic Radiation Spectrum

4. Properties of waves wavelength = λ frequency = ν speed = c c = speed of light 2.9979 x 108 m/s

5. Energies of a photon
Electromagnetic radiation travels in waves that are packaged into photons (quantum).
Given frequency (ν) or wavelength (λ) you can calculate the energy of a single photon.
E = hν = hc/λ
If the photon has energy does it have mass?
If an electron is in motion, does it have a λ?

6. Energy of the hydrogen emission lines
Each emission line is associated with a specific energy.
E = hc/λ

7. Hydrogen electron transitions

8. Bohr Model Electrons orbit the nucleus
Only certain orbits are allowed. (n=1,2,3, ∞)
Energy of the orbit is
En=-Z2RH/n2
Electrons move from one orbit to another by absorbing or emitting light.

9. Anonymous Evaluation Time
What have you liked so far about the course?
What suggestions do you have for improvement of the course?
Are you able to read the material presented on the chalk board and/or do you want more powerpoint talks?
What can Dr. Richmond do to help facilitate your learning?
What do you need to do to improve your course performance?
Other comments (TAs, quizzes, tests, homework, Lon-Capa, etc.)