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The Development of a New Atomic Model

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					The Development of a New
           Atomic Model
           Chapter 4 Section 1
             TEKS 2A, 2D, 2E;
          3A, 3C, 3E; 5A-B, 6A
4-1 Objectives
    Explain the mathematical relationship among
     the speed, wavelength and frequency of
     electromagnetic radiation.
    Discuss the dual wave/particle nature of light.
    Discuss the significance of the photoelectric
     effect and the line-emission spectrum of
     hydrogen to the development of the atomic
     model.
    Diagram and describe the Bohr model of the
     hydrogen atom.
  Super Fun
Chemistry Math!
   All forms of electromagnetic radiation move at a
    constant speed of 3.0 X 108 m/s (yeah, that’s the
    speed of light c).
   A wavelength λ is the distance between
    corresponding points on adjacent waves.
   Frequency f is the number of waves that pass a
    given point in one second.
   c = λf
   Remember E=mc2? That’s the same c.
Waves of Light
    Visible light is a form of electromagnetic
     radiation a form of energy that exhibits
     wavelike behavior as it travels through space.
    Other kinds of electromagnetic radiation
     include: X-rays, ultraviolet and infrared light,
     microwaves and radio waves. These waves
     have different wavelength, frequency, and
     energy limits.
    BRAIN WAVES are also a form of EMR.
Waves of Light




Radio waves, visible light, X-rays, and all the other parts of
the electromagnetic spectrum are fundamentally the same
thing, electromagnetic radiation.
 Waves of Light
Refer to Figure 4-1 on page 92 in your textbook for
specific wavelengths of the electromagnetic spectrum.
What wavelengths in the spectrum are visible to the
human eye?
Visible light is from ______ to ______.
 Waves of Light


Why do we have
to go to space to
see the complete
 electromagnetic
    spectrum?
Waves of Light

                   Electric and magnetic
                  fields oscillate together
                   but perpendicular to
                     each other and the
                   electromagnetic wave
                    moves in a direction
                 perpendicular to both of
                          the fields.
                                Particles of light
    A little bit of history…
   The photoelectric effect refers to the emission
    of electrons from a metal when light shines on
    the metal.
   Check out a cathode ray tube in Figure 4-3 on
    page 93.
   Light was already known to be a form of energy,
    but scientists couldn’t explain why light had to be
    of a minimum frequency for the photoelectric
    effect to occur.
                                Particles of light
    A little more history…
   1900, German physicist Max Planck studying
    the emission of light from hot objects figured it
    out…
   A quantum is the minimum quantity of energy
    that can be lost or gained by an atom for the
    photoelectric effect to occur.
   Planck’s Constant: h = 6.626 X 10-34 J*s
   E=hf       Energy of a quantum of radiation =
              (h) * frequency of radiation emitted
                            Particles of light
And yet more history…
   1905, Albert Einstein expanded on Planck’s
    theory by introducing the notion that EMR has
    a dual nature: both a wave and a particle.
   A photon is a particle of electromagnetic
    radiation having zero mass and carrying a
    quantum of energy.
   In the formula Ephoton=hf, Einstein explained
    the photoelectric effect. A photon particle
    with sufficient energy strikes the electrons.
                  Particles of light
And yet more history…
       WHOA NELLY!
I bet that this work led to
Einstein’s development of
   the theory of special
         relativity!
            E=mc2
Okay… enough already! My brainwaves
are oscillating at a low frequency

For classwork, due TODAY, October 22,
a few more questions…
Okay… enough already! My brainwaves
are oscillating at a low frequency

   What two objects have we studied that have a
    cathode and an anode and are used to study
    electron behaviors? (refer to p.70 and 93)
   Which wavelengths in the Electromagnetic
    Spectrum make up “visible light?” (p 92)
   What was the precursor to Einstein’s theory of
    special relativity, E=mc2, that disproved one part
    of Dalton’s Atomic Theory? (photons’ mass)
And just for joy
 In the electromagnetic spectrum, what is the
wavelength and frequency of your favorite color?

				
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posted:1/19/2013
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