chapter 04 structure of the atom general bibliography 1) various wikipedia, as specified 2)...
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![Page 1: Chapter 04 Structure of the Atom General Bibliography 1) Various wikipedia, as specified 2) Thornton-Rex, Modern Physics for Scientists & Eng, as indicated](https://reader035.vdocuments.mx/reader035/viewer/2022081420/56649d6a5503460f94a49248/html5/thumbnails/1.jpg)
Chapter 04Structure of the Atom
General Bibliography1) Various wikipedia, as specified
2) Thornton-Rex, Modern Physics for Scientists & Eng, as indicated
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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
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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.
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4.1 Geiger-Marsden-Rutherford
http://en.wikipedia.org/wiki/Geiger%E2%80%93Marsden_experiment
http://www.kutl.kyushu-u.ac.jp/seminar/MicroWorld1_E/Part2_E/P23_E/Geiger_Marsden_E.jpg
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4.2 Geiger-Marsden-Rutherford
2sin
1~
4
2221
KE
eZZratecount
Derivation on pages 131-137
Assume massive positive objectsCoulomb force
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4.2 Geiger-Marsden-Rutherford
Example 4.4 & 4.5: Estimate distance of closest approach for an alpha particle striking
an aluminum nucleusKE = 7.7 MeV
s
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4.3 Classical Atomic Model
r
v
Using Newtonian Mechanics & JJThomson’s anticipated sizes:
1. Estimate the speed of the orbiting electron
2. Total Energy of the system
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4.3 Classical Atomic Model
Failures of the classical model:
1.
2.
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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/2.
n=1
n=2 n=3
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4.4 Bohr Model
2
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4.4 Bohr Model
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4.5 Successes & Failures of Bohr Model
rseparationCoulomb
rrradiusorbit e
Reduced Mass Correction
ee
e
Mm
Mmmfixmagic
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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+
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4.6 Characteristic X-Ray Spectra
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4.7 Atomic Excitation