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Electromagnetic Radiation and the Bohr Model of the Atom

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Title: Electromagnetic Radiation and the Bohr Model of the Atom


1
Electromagnetic Radiation and the Bohr Model of
the Atom
  • Objective Students will understand the Bohr
    model of the atom by understanding light.

2
Review Rutherfords Model
3
Rutherfords Contributions
  • the nucleus of the atom is composed of protons
    and neutrons.
  • That the nucleus is small
  • The electrons are circling the nucleus.

4
Rutherfords Failure
  • He couldnt explain why the negative electrons
    arent attracted into the positive nucleus,
    causing the atom to collapse.
  • Video 1515

5
A Strange Answer to a Strange Question
  • Why doesnt the electron fall into the nucleus?
  • Because it isnt allowed!

To understand this unbelievable phenomenon, we
must understand the nature of light
6
Neils Bohr
We are all agreed that your theory is crazy. The
question which divides us is whether it is crazy
enough to have a chance of being correct. My own
feeling is that it is not crazy enough.
7
What are the components of a wave?
  • A wave has frequency, amplitude and wavelength

8
Frequency
  • The of peaks that pass by in a given amount of
    time
  • Hz 1/sec
  • MHz 1,000,000/sec
  • KHz 1,000/sec

9
Electromagnetic Radiation
  • Name Several Types of electromagnetic
    Radiation(325)

10
How do waves differ?
  • They have different wavelengths
  • They have different frequencies
  • They have different amplitudes

11
How are they different?
  • They have different frequencies
  • They also have different energies

Click here to see how they differ
Then here to see how they are the same!
12
What do they all have in common?
  • They all travel at the speed of light
  • 3.00 x 108 meter/sec

13
Wavelength and Frequency
  • If the ? 2 meters and ? 10/sec, find the
    speed
  • ? x ? speed
  • 2 meters x 10/sec 20.0 meters/sec
  • 5 meters x ______ 20.0 meters/sec
  • So frequency and wavelength are inversely
    proportional

14
KSL Radios Wavelength
  • KSL broadcasts at 1160 KHz. Find the ? of KSLs
    signal.
  • 1160KHz 1160000 /sec
  • Wavelength x frequency speed
  • ? x 1160000 3.0 x108 m/sec
  • (3.0 x108 m/sec)/(1160000/sec) 258 meters

15
FM or AM
16
What is a Photon
  • Photons are light particles. A bundle of energy

17
Energy of Photons
  • The energy of a photon is given by this equation
    E ? h.
  • The symbol h represents Plancks constant. It
    has a value of

18
KSL 1160
  • Find the Energy of a photon of light produced by
    KSL (1160 KHz)
  • E ? h
  • E 1160000 s-1 x 6.626 x 10-34 Js
  • E 7.69 x 10-28 J

19
Energy and Frequency
  • How are Energy and ? related?
  • The higher the frequency the greater the energy.
  • How are Energy and ? related?
  • The lower the energy the longer the ?

20
Radio Waves
  • Turn your book to page 325. What is the
    electromagnetic with the lowest energy?

21
Who or what is Roy G Biv?
  • An acronym for the colors of the rainbow. It is
    not a person.

22
Hydrogen and Roy G Biv
  • The colors emitted when energy is passed through
    hydrogen is

23
The Quantum Atom
  • Atoms are quantized because they only emit light
    at certain frequencies and energies.
  • A Quantum is the smallest quantity of radiant
    energy, equal to Planck's constant times the
    frequency of the associated radiation.
  • E h x frequency

24
(No Transcript)
25
A Staircase Not a Ramp
  • Look at pg 330 Figure 11.15. Like a staircase,
    the atom has specific energies. A ramp has
    infinitely small divisions.

26
What Does N represent?
  • The Energy Levels inside the atom

27
What values can N have
  • 1, 2, 3, .
  • In the hydrogen atom, where does the electron
    reside?
  • In the lowest energy level or n1
  • The electron can move up to higher energy levels
    by absorbing photons.
  • We then say the electron is excited

28
A relaxing electron
  • What happens when an electron relaxes?
  • It falls from a high energy level to a lower one.
  • What happens to the extra energy?
  • It is emitted in the form of light.
  • The further an electron falls the more energy it
    gives off

29
What Gives off the Most Energy?
Higher Energy
Lower Energy
30
Finding the energy of n3
  • The equation to find the energy of the hydrogen
    energy levels is
  • E -2.178 x 10-18 J (1/N2)
  • E -2.178 x 10-18 J (1/32)
  • E -2.42 x 10-19 J

31
Finding the difference between n2 and n3
  • For N2, E -5.45 x 10-19 J
  • For N3, E -2.42 x 10-19 J
  • What happens if an electron falls from N3 to
    N2?
  • Just take n2 and subtract n3, that gives you ?E
  • ?E 3.0 x 10-19 J

32
Calculate the ?
  • E ? h
  • 3.03 x 10-19 J ? h
  • 3.03 x 10-19 J ? x 6.626 x 10-34Js
  • ? 4.57x 1014 Hz
  • ? x ? 3.03 x 108 meters/sec
  • ? x 4.57x 1014 3.0 x 108 meters/sec
  • ? 6.56 x 10-7 meters

33
The Lyman and Balmer series
  • If an electron falls to n1, the energy is to
    high for us to see.
  • It can be detected but it falls into the UV
    spectrum

34
Ultra Violet, Infra Red, Visible
  • Where the electron falls to determines the type
    of light it produces.
  • If it falls to the n3, it produces IR.
  • We can only se it if it falls to the n2

35
The absorption Spectrum
36
Quiz 1
  • 1. What was the shortcoming of the Rutherford
    model of the atom?
  • a. It couldnt explain how the electron stayed in
    orbit.
  • b. It couldnt explain the existence of
    electrons.
  • c. It couldnt explain the existence of protons.

37
  • 2. Who improved the Rutherford model?
  • a. Dalton
  • b. JJ Thompsonc. Neils Bohr
  • d. Max Plank

38
  • 3. Who is the constant h named after?
  • a. Dalton
  • b. JJ Thompsonc. Neils Bohr
  • d. Max Plank

39
  • 4. Which has the longest wavelength?
  • a. Red Light
  • b. UV Lightc. IR Light
  • d. Violet Light

40
  • 5. Which form of electromagnetic energy has the
    most energy?
  • a. Red Light
  • b. UV Lightc. IR Light
  • d. Violet Light

41
  • 6. Which elements spectrum did Bohr explain?
  • a. Helium
  • b. Hydrogenc. Carbon
  • d. Oxygen

42
  • 7. Which has the lowest energy in the visible
    spectrum?
  • a. Red Light
  • b. UV Lightc. IR Light
  • d. Violet Light

43
  • 8. Who found energy levels in the atom?
  • a. Dalton
  • b. JJ Thompsonc. Neils Bohr
  • d. Max Plank

44
  • 9. W?
  • a.
  • b. c.
  • d.

45
  • 10. Which electronic transition gives off the
    most energy in the hydrogen atom?
  • a. N2 to N1
  • b. N3 to N2c. N4 to N3
  • d. N4 to N2
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