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09 - π 2 m e e 4/h 2(E(n are called energy levels n = 1 is...

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Lecture 9 => Review of Lecture 8: Planck proposes that the vibrational energy in heated solids is quantized (not continuous) =>E vib = nh ν . Then can predict entire black body radiation curve, if h has the value 6.62 x 10 34 J s Photoelectric effect: Einstein proposes new concept to explain experiments. Light energy comes in bundles (now called photons) ε ph = h ν . Photons are absorbed one at a time and if ν > ν crit then electrons can be ejected from a metal. Ionization energy (work function) is the minimum energy required to do so (h ν crit ). Neils Bohr, using a simple planetary like model of the atom, proposes that the angular momentum of electrons “orbiting” the nucleus in hydrogen like atoms is quantized: m e rv = nh. Then can calculate the binding energy of one electron to a nucleus of charge +Ze:
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E(n) = R H Z 2 /n 2 where R H = 2.179 x 10 18 J = 4
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Unformatted text preview: π 2 m e e 4 /h 2 (E(n) are called energy levels) n = 1 is the “ground state”. n > 1 are excited states. Electrons in atoms can absorb energy only in specific increments. Input energy can be from a photon or from sufficiently energetic collisions with hot atoms or electrons in a discharge (from a large applied voltage). Excited state electrons eventually “relax” to the ground state (some times in multiple steps), emitting photons to conserve energy. Lyman, Balmer, Paschen, … series. Changing energy level by interaction with light: Δ E = E(n initial ) – E(n final ), if + photon emitted, if – photon absorbed. Ψ 2 These could represent Ψ 2 or Ψ Ψ 2 Ψ 2 Ψ One radial node and one angular ( θ = 90 o ) node One radial node and two angular ( θ = 90 o ) nodes All show Ψ...
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