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ZCT104 CHAPTER 5 : ATOMIC MODEL, RH is called the Rydberg constant, image,…

- - - - Atoms emit and absorb EM radiation
  - - - shows ‘finger print’ emission spectral lines of H, Hg and Ne.
      - shows absorption lines for H
- - - - prediction has been falsified because observationally, light spectra from all atoms, have sets of discrete spectral lines correspond to many different frequencies
      - light emitted from the atom in the plum-pudding model is predicted to have exactly one unique frequency
- - - - An electron in an atom moves in a circular orbit about the nucleus under Coulomb attraction obeying the law of classical mechanics.
        
        Coulomb’s attraction = centripetal force
    - - possible for an electron to move in an orbit that contains an integral number of de Broglie wavelengths
        
        Quantization of angular momentum
    - - quantization of angular momentum and the equation of mechanical stability
    - - EM radiation is emitted if an electron initially moving in an orbit of total energy Ei, discontinuously changes it motion so that it moves in an orbit of total energy Ef ,(Ei > Ef).
        
        Kinetic energy
        
        Adding up KE + V, we obtain the total mechanical energy of the atom:
        
        The ground state energy
        
        Quantization of energy levels
        
        “principle quantum number”
        
        the Bohr radius, r0 = 0.53Å
        
        the ground state energy of the hydrogen atom,
        E0 = -13.6 eV
        
        Bohr’s 4th postulate explains the line spectrum
- - - - Ratom ~ 10-10m
        Rnucleus ~ 10-13 - 10-15 m
      - Infrared catastrophe: insufficiency of the Rutherford model
- - - - As V increases, the current measured also increases.
      - The measured current drops at multiples of a critical potential.
      - V = 4.9 V, 9.8V, 14.7V