Quantum Model of the Atom by XVgRWo

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									Quantum Model of the Atom

 Bohr
 de Broglie
 Heisenberg
 Schrödinger
Neils Bohr (1885 –1962)

Bohr Model
   of the
 Hydrogen
   Atom
         Bohr model of the atom
                        In the Bohr
                            model,
                          electrons
                           can only
Energy




                            exist at
                           specific
                        energy levels
                            (orbit).
Photo Absorption and
      Emission
Hydrogen Line Spectrum




                Balmer Series
Line Spectra
 Line spectrum of Hydrogen is
   produced when an electron
   drops from a higher-energy
   orbit to a lower energy orbit.
       Specifically,
    Ephoton = E2 - E1 = h 
Bohr Checked it with Math.
 Used  mass and charge of the
  electron together with Planck’s
  constant and calculated where
  the spectral lines should be and
  they were!
 Problem -- only worked for
  Hydrogen!
      Bohr model of the atom
   The Bohr model is a
    ‘planetary’ type
    model.

   Each principal
    quantum represents
    a new ‘orbit’ or layer.

   The nucleus is at the
    center of the model.
Hydrogen Spectrum (cont.)
Each line of the Hydrogen
 spectrum is produced by
  and corresponds to the
 emission of photons with
 specific energies (E = h)
   Bohr Model
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What the Heck is Light?
         Hold It!
 Nay, Nay says “Classical”
  theory.
 Hydrogen should be excited by
  whatever amount of energy.
 Should be continuous spectrum
 What’s with the lines????
 Why   wouldn’t there be an
  infinite number of energy levels
  for electrons?
 Photoelectric effect and
  Hydrogen spectrum.
Neils Bohr (1885 –1962)

Bohr Model
   of the
 Hydrogen
   Atom
       Louis de Broglie
         (1892-1987)
Electrons should
  be considered
 waves confined
   to the space
    around an
 atomic nucleus
The Quantum Atom (cont.)

 Since electrons are waves,
  they can amplify and cancel
  out when in and out of sync.
 Therefore only certain
  energies of electrons are
  possible.
    Werner Heisenberg
 Heisenberg
  Uncertainty
Principle – It is
 impossible to
 determine the
  position and
 velocity of an
    electron
simultaneously.
Separated at Birth….
   Heisenberg uncertainty
         principle
   order to observe an electron,
 In
 one would need to hit it with
 photons having a very short
 wavelength.
 Shortwavelength photons
 would have a high frequency
 and a great deal of energy.
   Heisenberg uncertainty
         principle
 Ifone were to hit an electron, it
  would cause the motion and the
  speed of the electron to change.
 Lower  energy photons would
  have a smaller effect but would
  not give precise information.
Heisenberg Uncertainty
      Principle


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     Erwin Schrödinger
        (1887-1961)
 Schrödinger
 developed the
   calculus to
  describe the
wave behavior
and energies of
  electrons in
     atoms.
Schrödinger’s Equation




     Yeah, but
      it works!
  Bohr vs. Schrödinger
  Orbits vs. Orbitals
Bohr -- definite
 distinct orbits
 populated by
    electron
   particles.
  Bohr vs. Schrödinger
   Orbits vs. Orbitals
Schrödinger -- electron are
 waves (de Broglie) with a
     certain probability
  (mathematical model) of
    being found in three
dimensional regions around
   the nucleus - orbitals
Comparing Models of the
   Atom – A review


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