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28.1 Quantum Mechanics Unanswered questions from Bohr’s model: Spectra of other elements.

28.1 Quantum Mechanics Unanswered questions from Bohr’s model: Spectra of other elements. The fine structure of emission lines. Some spectral lines are brighter than others. Bonding of molecules, solids or liquids. Classical theories fail to explain these observations

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28.1 Quantum Mechanics Unanswered questions from Bohr’s model: Spectra of other elements.

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  1. 28.1 Quantum Mechanics • Unanswered questions from Bohr’s model: • Spectra of other elements. • The fine structure of emission lines. • Some spectral lines are brighter than others. • Bonding of molecules, solids or liquids. • Classical theories fail to explain these observations • Space and time description of atoms is not possible • Experiments do not show true nature of atoms, just an approximation. APHY202

  2. 28.2 The Wave Function and Young’s Experiment • What corresponds to the amplitude of a matter wave? • The wave function (Ψ) which may vary in magnitude from point to point in space and time • If Ψ is for a single electron then Ψ2 is the probability of finding the electron at a given position and time. • Using electrons, you will find an interference pattern similar to that formed by waves. APHY202

  3. 28.3 The Heisenburg Uncertainty Principle • A limit to the accuracy of measurements on the atomic scale ћ = 1.055 x 10-34 Js APHY202

  4. 28.5 Quantum Mechanical View of Atoms APHY202

  5. 28.6 Quantum Numbers • Principle: n = 1 → ∞ • Total energy of each state • Orbital: 0 ≤ l ≤ n-1 • Magnitude of the electron’s angular momentum • Magnetic: - l ≤ ml ≤ l • Direction of the electron’s angular momentum • Zeeman effect • Spin: ms = ± ½ • Fine structure APHY202

  6. 28.7 Complex Atoms and the Exclusion Principle • Mathematically difficult due to electron repulsion • The energy levels depend on n and l • Atomic number Z • Pauli exclusion principle APHY202

  7. 28.10 Fluorescence and Phosphorescence • Fluorescence: the absorbed photon is UV and the emitted photons are visible. • Phosphorescence: atoms are in a metastable state APHY202

  8. 28.11 Lasers • Conditions to produce a laser beam: • You must have more atoms in an excited state than in the ground state. • The excited state must be metastable. • The emitted photons must be contained long enough to continue to stimulate other atoms. • Coherent, monochromatic, narrow beam APHY202

  9. 28.11 Lasers • Absorption, Excited State • Stimulated Emission APHY202

  10. 28.11 Lasers • Applications APHY202

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