# The Development of a New Atomic Model by pptfiles

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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
   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
   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
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
are oscillating at a low frequency

For classwork, due TODAY, October 22,
a few more questions…
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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