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.
31/03/2021
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Atomic Models: Electrons, Photons, and Atoms - Lecture Slides, Lecture notes of Physics
atomic and molecular physics for undergraduate students for 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. 31/03/
What we have learned? Discovery of electron and proton: ▪ Millikan’s oil drop experiment measured the charge (e) of an electron e = - 1.6 x 10
- 19 C m = 9.1 x 10 - 31 kg ▪ Rutherford discovered the proton in the gold foil experiment. ▪ Various experiment showed that the mass of nucleus is apparently twice than the number of proton in nucleus.
What is the origin of these additional mass?
▪ Rutherford postulated the existence of some neutral particle having mass similar to the proton, but there was no direct experimental evidence.
Constituents of an atom:
Electron - 1.6 x 10 - 19 C m= 9.1 x 10-31 kg
Proton +1.6 x 10-19 C m= 1.672 x 10-27 kg
Neutron 0 C m= 1.674 x 10-27 kg
▪ Newton: discovered that, sun light when allowed to pass through prism was decomposed into a beautiful band of color called spectrum. Newton explained that this light itself is composed of many colors. ▪ Kirchhoff : The ratio between power of emission and the power of absorption for light of the same wavelength is constant for all bodies at the same temperature. ▪ Balmer : gave an empirical formula for hydrogen spectrum.
2. Planck’s quanta
Bohr 1913
Combined the concepts of:
a. Different atoms and molecules can emit or absorb energy in discrete quantities only. The smallest amount of energy that can be emitted or absorbed in the form of electromagnetic radiation is known as quantum. b. The energy of the radiation absorbed or emitted is directly proportional to the frequency of the radiation.
- Einstein’s photons
Bohr 1913
Combined the concepts of: a. That light is composed of corpuscles or photons, the energy of which is given by Planck’s relationship. b. An atom in the metal can absorb either a whole photon or nothing.
Bohr 1913
▪ How did Bohr determine the allowed energy levels for electrons?
▪ How did Bohr determine the frequency of light emitted in a transition b/w two energy levels?
Copyright © 2015, W. W. Norton & Company Prepared by Dr. Mai Khaleel, Isra University CHAPTER 1: Electrons, photons, and atoms This concludes the Lecture slides for Physics of Atoms and Molecules B. H. Bransden (Author), Charles J.