AP Chemistry Unit 3.12 Photoelectric Effect

Photoelectric Effect

  • Photoelectric Effect: the wavelength of the photon is related to the frequency of the radiation
  • When a photon is absorbed or emitted by an atom or molecule, energy is increased or decreased by an amount equal to the energy of the photon

Planck’s Constant

  • Planck’s Constant: defines the quantum nature of energy and relates the energy of a photon to its frequency
    • Energy can only be gained/lost in whole-number multiples of hv (h is planck’s constant)
    • Quantum: small “packets” of energy

PES Graphs

  • Used to measure ionization energies (binding energies)
    • Valence shell has the least binding energy
    • Highest binding energy = closest to the nucleus
  • Each peak represents electrons in a sublvl → the height of the peak corresponds to the number of electrons in each sublevel
    • Always label peaks with sublevels; all electrons in the same sublvl have same binding energy
  • When asked to draw peak, take into account nuclear charge (how many protons)
    • Remember: Nuclear charge increases down a group & across a period → if nuclear charge is stronger then the peak will be more left
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