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The Bohr Atom

The Bohr Atom. Stuff. A change ……. Monday April 24 topics: Quantum Theory read: chapter 39, sections 1 through 6 Wednesday April 26 topics: Matter Waves read: chapter 24, sections 1 through 4. Reading Question. The Bohr model successfully explained the spectrum of.

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The Bohr Atom

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  1. The Bohr Atom

  2. Stuff A change …… Monday April 24 topics: Quantum Theory read: chapter 39, sections 1 through 6 Wednesday April 26 topics: Matter Waves read: chapter 24, sections 1 through 4

  3. Reading Question The Bohr model successfully explained the spectrum of 1. hydrogen. 2. helium. 3. hydrogen and helium. 4. all the naturally occurring elements. 5. all the elements in the periodic table.

  4. Reading Question The Bohr model successfully explained the spectrum of 1. hydrogen. 2. helium. 3. hydrogen and helium. 4. all the naturally occurring elements. 5. all the elements in the periodic table.

  5. Reading Question What is the name of the diagram used to represent the stationary states of an atom? 1. Atomic-state diagram 2. Energy-level diagram 3. Standing wave diagram 4. Atomic orbital diagram 5. Feynman diagram

  6. Reading Question What is the name of the diagram used to represent the stationary states of an atom? 1. Atomic-state diagram 2. Energy-level diagram 3. Standing wave diagram 4. Atomic orbital diagram 5. Feynman diagram

  7. Reading Question Cite one experiment that confirms the de Broglie hypothesis. 1. Spectrum of blackbody radiation 2. X-ray penetration depth 3. Electron diffraction 4. Optical pumping 5. Nuclear magnetic resonance

  8. Reading Question Cite one experiment that confirms the de Broglie hypothesis. 1. Spectrum of blackbody radiation 2. X-ray penetration depth 3. Electron diffraction 4. Optical pumping 5. Nuclear magnetic resonance

  9. Reading Question The intensity of a beam of light is increased but the light’s frequency is unchanged. Which of the following is true? 1. The photons travel faster. 2. Each photon has more energy. 3. There are more photons per second. 4. The photons are larger.

  10. Reading Question The intensity of a beam of light is increased but the light’s frequency is unchanged. Which of the following is true? 1. The photons travel faster. 2. Each photon has more energy. 3. There are more photons per second. 4. The photons are larger.

  11. Bohr Atom • Atomic Spectra Throughout the nineteenth century many new elements were discovered by their spectra.

  12. Bohr Atom • Balmer Spectral Lines hydrogen

  13. Bohr Atom • Nuclear Atom

  14. Bohr Atom • Classical Atom electron e-m radiation Classical atom was unstable and emitted radiation of all wave lengths

  15. Bohr Atom Solve the L equation for v and substitute into the F equation Substitute r into the L equation and solve for v

  16. n=3 n=2 E2 = -3.4eV E1 = -13.6eV n=1 Bohr Atom • What is the energy of the atom? Substitute r and v into the E equation

  17. Bohr Atom

  18. Bohr Atom ultravilot visible infrared

  19. Bohr Atom

  20. Bohr Atom • You will recall that Max Planck proposed energy quantization to explain blackbody radiation and Albert Einstein proposed light quantization (photons) to explain the photoelectric effect, what did Niels Bohr propose to explain the spectra of hydrogen? • Write the equation for his quantum condition. angular momentum quantization

  21. Bohr Atom • Using this quantum condition and classical Newtonian physics Bohr found that the energy and orbits were quantized. What is the equation that explains the quantization of energy? Write both forms.

  22. - 13.6 eV/9 = - 1.5 eV - 13.6 eV/16 = - 0.84 eV Bohr Atom • Use this equation to calculate the energy for the first four energy levels. E1 = E2 = E3 = E4 = • What is the energy for n = ∞? E∞ = • What is the significant of the fact that the energy is negative? Discuss this in your group. - 13.6 eV - 13.6 eV/4 = - 3.4 eV 0

  23. n = 3 n = 2 n = 1 Bohr Atom • Below is the start of an energy level diagram. Draw the first four energy levels and n = ∞ on the diagram. The three dash lines are to help you place the energy levels at the correct energy. Label each level with the quantum number and energy value (in eV) for that level.

  24. Bohr Atom • Assume an electron is in the n = 3 state, what is the energy of the atom (electron)? • The electron “jumps” to the ground state and emits a photon. What is the energy of the atom now?

  25. Bohr Atom • Use the energy of these two states to find the frequency of the photon. • What is the wavelength of the photon? • Is the photon in the visible range? Can we see the photon? Ultraviolet so we can not see the line.

  26. Bohr Atom • The electron’s orbits are also quantized. What is the equation that describes the orbits? Write this equation in two forms: one with fundamental constants and one with a value in nm. • Below is a drawing of the first Bohr orbit. This is also called the ground state orbit. Use the equation to draw the next three orbits. Label the orbits with their quantum number.

  27. Bohr Atom • Draw an arrow on the orbits to represent the electron “jumping” from the n = 3 orbit to the ground state (n = 1).

  28. Bohr Atom • Assume the electron is in the ground state and a photon with a wavelength of 97.3 nm is absorbed by the atom. What happens to the atom or electron? Discuss this. What is the final state of the atom? • Now assume the photon has a wavelength of 112.2 nm. What happens to the atom or electron? Discuss this in your group. • What if the photon has a wavelength of 90.1 nm? Discuss this in your group.

  29. Student Workbook

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  38. Class Questions A photon with a wavelength of 414 nm has energy Ephoton = 3.0 eV. Do you expect to see a spectral line with = 414 nm in the emission spectrum of the atom represented by this energy-level diagram? If so, what transition or transitions will emit it?

  39. Class Questions A photon with a wavelength of 414 nm has energy Ephoton = 3.0 eV. Do you expect to see a spectral line with = 414 nm in the emission spectrum of the atom represented by this energy-level diagram? If so, what transition or transitions will emit it?

  40. Class Questions A photon with a wavelength of 414 nm has energy Ephoton = 3.0 eV. Do you expect to see a spectral line with λ = 414 nm in the absorption spectrum of the atom represented by this energy-level diagram? If so, what transition or transitions will absorb it?

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