Transcript Power Point

Modern Chemistry
Chapter 4
Arrangement of Electrons
in Atoms
Sections 1-3
The Development of a New Atomic Model
The Quantum Model of the Atom
Electron Configurations
1
Section 1
The Development of
a New Atomic Model
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Section 1 Vocabulary
Electromagnetic radiation
Electromagnetic spectrum
Wavelength
Frequency
Photoelectric effect
Quantum
Photon
Ground State
Excited state
Line-emission spectrum
Continuous spectrum
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Properties of Light
• Electromagnetic Radiation: a form of
energy that exhibits wavelike behavior
as it travels through space.
• Wavelength: the distance between
corresponding points on adjacent waves
• Frequency: the number of waves that
pass a given point in a specific time.
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Wavelength and Frequency
Image
p. 98
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p. 98
Electromagnetic Spectrum Image
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Electromagnetic Spectrum Image
p. 98
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Properties of Light
• wavelength x frequency = speed of light
•

x

=
• Visible Light = R O Y G B I V
Long 
Low 
Low E
c
Short 
High 
High E
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The Photoelectric Effect
• Max Planck proposed that energy is
proportional to the frequency of the
electromagnetic wave.
• Electromagnetic energy is emitted from
objects in small packages called quanta.
• E=h
• Planck’s constant
–h = 6.626 x 10-34 J•sec
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Quanitization of Energy
Animation
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The Photoelectric Effect
• Albert Einstein expanded on Planck’s
idea.
• Electromagnetic radiation has a dual
wave-particle nature.
• A particle of light is a photon.
• Photon: a particle of electromagnetic
radiation having zero mass and carrying
a quantum of energy.
• Ephoton = h 
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Energy of a Photon Animation
p. 98
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The Photoelectric Effect
p. 99
• The photoelectric
effect refers to
the emission of
electrons from a
metal when light
shines on the
metal.
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Photoelectric Effect Animaiton
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The Photoelectric Effect
To knock an electron loose,
it must be hit with a photon which
possesses a minimum amount of energy.
This energy corresponds to its frequency.
Different metals hold electrons
more or less tightly
So different metals require
different frequencies to
show the photoelectric
effect.
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The H-Atom’s Line Emission Spectrum
p. 101
• Electric current is
passed through a
vacuum tube with
hydrogen in it.
• A glow is produced
• When shined
through a prism a
line emission
spectrum is
produced
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Hydrogen’s Line Emission Spectrum
Insert Glencoe Disk 1
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Absorption and Emission
Spectrum Animation
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Line Emission Spectrum
Insert Glencoe Disk 1
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Bohr Model of the Atom
• Niels Bohr proposed orbits for the
electrons
• Each orbit has a fixed energy
• Lower energy orbits are closer to the
nucleus
• Between orbits the
electron cannot exist
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Explaining the Line Emission Spectrum
An electron absorbs a specific amount of
energy (absorption) and moves from its
ground state to an excited state
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Explaining the Line Emission Spectrum
The electron returns to its ground state
and emits a photon (emission).
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Explaining the Line Emission Spectrum
This photon has an energy corresponding
to the difference between the two
states.
This photon has a specific E, ,  and
color.
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Photon Emission and Absorption
Image
p. 102
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Bohr Model of the Atom
• Bohr’s calculated values for the lines
agreed with the values observed for the
lines in each series.
• However, it did not explain the spectra
of atoms with more than
one electron.
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Bohr Model of the Atom
Animation
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Bohr and Einstein
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Section 1 Homework
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