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Lecture 8: Matter and Energy - Sub-atomic Structure Review

This lecture covers topics such as temperature, heat, and thermal energy, the energy stored in atoms, atomic energy states, the development of the atomic model, the discovery of the electron and atomic nucleus, the wave nature of light, spectroscopy, Balmer's formula, the Bohr model of the hydrogen atom, and the quantum view of the atom.

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Lecture 8: Matter and Energy - Sub-atomic Structure Review

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  1. Lecture 8: Matter and Energy sub-atomic structure

  2. Review from Last Time: • temperature, heat, and thermal energy • mass as a form of energy • atoms and elements • phases of matter

  3. New Energy Unit • unit of energy for talking about atoms: electron volts (eV) 1 eV = 1.60 x 10-19 Joule

  4. The energy stored in atoms • ground state – lowest energy • excited state – higher energy • ionization – electron lost

  5. Atomic Energy States

  6. Atomic Energy States are Quantized

  7. Allowed energy levels for Hydrogen

  8. Developing the model of the Atom • electrons discovered by J.J. Thomson in 1857 using an experiment with “cathode rays” • the atomic nucleus discovered in 1910 by Rutherford • Bohr model of the energy levels of Hydrogen developed (early 1900’s) • study of the atom led to the “quantum revolution”

  9. Cathode ray tube

  10. Discovery of the electron “I see no escape from the conclusion that [cathode rays] are charges of negative electricity carried by particles of matter” J.J. Thomson

  11. Rutherford’s Experiment “It is as though one fired a 15 inch shell at a piece of tissue paper and it came back and hit you.”

  12. Rutherford’s Model of the Atom

  13. Light is a wave

  14. Wavelength, Frequency, and Amplitude amplitude is the height of the wiggles

  15. How do we know light is a wave? Young’s Double-Slit Experiment

  16. The Spectrum of the Sun

  17. The Kirchhoff-Bunsen Experiment

  18. The Spectrum of Hydrogen Emission Spectrum Absorption Spectrum

  19. Spectra of some other elements Helium Sodium Neon

  20. Balmer’s formula for the spectral lines of Hydrogen 1/l = R (1/4 – 1/n2) where n = 3, 4, 5, 6, … R is a constant

  21. The Bohr Model of the Hydrogen Atom

  22. Bohr’s equation for Hydrogen 1/l = R (1/n2 – 1/m2) l = wavelength n = number of inner orbit m = number of outer orbit R = Rydberg constant  reduces to Balmer’s formula when n=2

  23. A Modern Picture of Energy Levels

  24. The quantum view of the atom • observation: An atom will only absorb or release light at discrete frequencies • explanation: • absorption or emission of light is caused by electron energy transitions within the atom • the energy carried by light is connected with its frequency • electrons are only allowed to move between discrete energy levels in the atom

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