1. Chapter 04 Structure of the Atom
General Bibliography
1) Various wikipedia, as specified
2) Thornton-Rex, Modern Physics for Scientists & Eng, as indicated

2. Outline 4.1 Atomic Models of Thomson & Rutherford
4.2 Rutherford Scattering
4.3 Classical Atomic Model
4.4 Bohr Model
4.5 Failures of the Bohr Model
4.6 Characteristic X-Ray Spectra
4.7 Atomic Excitations

3. with negative ‘raisins’
4.1 Plum Pudding Model
J.J. Thomson
Positive pudding
with negative ‘raisins’
Electrons oscillate about
their equilibrium position
when heated and produce
EM radiation
If made oscillations about ~10-10 m,
could produce visible wavelengths, but never line spectra.

4. 4.1 Geiger-Marsden-Rutherford
2. Radium alpha source, gold foil, ZnS screen, microscope.
3. Plum pudding model expect heavy alpha particles to plow through the pudding. If the alphas hit an electron, the deflection angles will be very small, R&T do a back-of-the-envelope calculation and get about 1deg of deviation with each collision.
4. Geiger & Marsden observed lots of particles bouncing to larger angles.

5. 4.2 Geiger-Marsden-Rutherford
Assume massive positive objects
Coulomb force
Derivation on pages

6. 4.2 Geiger-Marsden-Rutherford
Example 4.4 & 4.5: Estimate distance of closest approach for an alpha particle striking an aluminum nucleus
KE = 7.7 MeV s

7. 4.3 Classical Atomic Modelv r
Using Newtonian Mechanics & JJThomson’s anticipated sizes:
1. Estimate the speed of the orbiting electron
2. Total Energy of the system

8. 4.3 Classical Atomic Model
Failures of the classical model: 1. 2.

9. 4.4 Bohr’s Postulates
A countable number of “stationary states” exist. (electrons in a selection of allowed orbit radii)
EM radiation emitted when electron jumps/transitions between states
Classical rules apply to stationary states, but not during transitions between states.
…Angular momentum occurs in integer multiples of h/2p.
n=1
n=2
n=3

10. 4.4 Bohr Model

11. 4.4 Bohr Model

12. 4.5 Successes & Failures of Bohr Model
Reduced Mass Correction

13. 4.5 Successes & Failures of Bohr Model
+ Rydberg Eqn predicts many lines of He (except for a few extra lines)
Higher resolution diffraction gratings in advanced spectrographs indicated some transitions were multiple (fine structure)
Bohr’s “n” quantum number is only partially associated with angular momentum (1s, 2s, 3s,… states do not have angular momentum)
Worked best for single-electron atoms
H+, He+, Li+

14. 4.6 Characteristic X-Ray Spectra

15. 4.7 Atomic Excitation