Copyright © 2015, W. W. Norton & Company
Prepared by Dr. Mai Khaleel,
Isra University
Lecture Slides
CHAPTER 1: Electrons, photons, and atoms
Physics of Atoms and Molecules
B. H. Bransden (Author), Charles J.
24/03/2021
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Atomic Models: A Historical Perspective - Lecture Slides, Lecture notes of Physics
atomic and molecular physics for undergraduate students. physics major
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2020/2021
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Copyright © 2015 , W. W. Norton & Company Prepared by Dr. Mai Khaleel, Isra University
Lecture Slides
CHAPTER 1 : Electrons, photons, and atoms Physics of Atoms and Molecules B. H. Bransden (Author), Charles J. 24 / 03 / 2021
1897 Thomson
“Plum Pudding” or “Chocolate Chip Cookie” Model positive (evenly distributed) “dough” part negative “chocolate”
1897 Thomson
Thomson used a cathode ray tube to deduce the presence of a negatively charged particle: the electron.
1897 Thomson
Cathode Ray Tube: CRT
1897 Thomson
Experiment 2 : Electric deflection Conclusions As the cathode rays carry a charge of negative electricity, are deflected by an electrostatic force as if they were negatively electrified and are acted on by a magnetic force in just the way in which this force would act on a negatively electrified body moving along the path of these rays, I can see no escape from the conclusion that they are charges of negative electricity carried by particles of matter.
1897 Thomson
Experiment 3: Mass-to-charge (e/m) ratio Conclusions Thomson named these particles as corpuscles. He concluded that the corpuscles were smaller than the size of the atoms and were an integral part of an atom.
1897 Thomson
Based on the experimental results Thomson also proposed his plum
pudding model. He was honored the Nobel Prize in Physics.
1916 Robert Millikan
- Measured the charge of the electron in his
famous experiment that is a Millikan oil
drop experiment.
- | e |= 1.59 x 10
- 19
C
- How the experiment was done?
1908 Rutherford
- In 1909 , Rutherford discovered proton in his famous gold foil experiment.
- How the experiment was done?
1908 Rutherford Rutherford’s findings:
- Most of the particles passed right through
- A few particles were deflected
- VERY FEW were greatly deflected
- VERY FEW bounced back. Conclusions: 1 .The nucleus is small
- The nucleus is dense
- The nucleus is positively charged Atomic model: The atom had a dense positive core, with the rest composed of mostly empty space with the occasional negatively charged electron