Transcript Powerpoint Ch 7 - LTCConline.net

Chapter 7
Atomic Structure and Periodicity
7.1-7.2
7.3-7.4
7.5-7.8
7.9-7.11
7.13
Properties of Light
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Electromagnetic radiation- the way
energy travels through space.
This energy travels at the speed of
light.
Waves
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Three characteristics:
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1.Wavelength
2.Frequency
3. Speed
Wavelength =distance between two peaks (in meters)
Frequency = number of waves per second (cycles per
second)
Speed= travels at speed of light (meters per second)
continued
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Inverse relationship b/t. frequency and
wavelength.
Examples:
7.2 Nature of Matter
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Planck discovered:
Energy is gained or lost in whole
number quantities of hv
Planck’s constant h = 6.626 x 10-34 J.s
So Planck determined that energy is
quantized (measured) in small packets
called hv.
Energy of a Photon
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Change in energy can be calculated by:
Delta E = nhv
n = intergers (1,2,3…)
h = 6.626x10-34 J.s (Planck’s constant)
v = frequency of EM radiation absorbed
or emitted.
A Photon
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Einstein viewed electromagnetic
radiation as travelling in a stream of
particles called “photons”
E photon = hv= hc/lamda
To summarize….
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Energy is quantized. It occurs in units
called quanta.
Electromagnetic radiation exhibits
wavelike properties and particulate
properties also.
deBroglie equation
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EM radiation shows wavelike and
particulate properties.
Electrons exhibit particulate and
wavelike properties.
m = h/lamdav or lamda = h/mv
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Examples:
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7.3 Atomic Spectrum of Hydrogen
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Excited hydrogen atoms emit light!
Hydrogen bonds are broken and H
atoms release energy….
Excess energy is released by emitting
light of different wavelengths.
Figure 7.7 A Change Between
Two Discrete Energy Levels
Emits a Photon of Light
Figure 7.8
Electronic
Transitions in
the Bohr Model
for the
Hydrogen Atom
Line Spectrum vs. Continuous
Bohr proposed that an electron orbits
the nucleus in a rigidly defined energy
level.
Energy Atom = E photon = E e-final- E e-initial
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Continuous Spectrum
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White light is a contiuous spectrum.
The Hydrogen Emission Spectrum is a
LINE spectrum
Atoms in excited states exhibit line
spectrum not continous spectrum.
Bohr model cont’d
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E = -2.178 x 10-18(Z2/n2)
Z= nuclear charge
n = the size of the radius (the larger the value of
n, the larger the orbit radius)
(-) sign means: energy of the electron bound
to the nucleus is lower than if electron were
at infinity.
At infinite distance, no interaction occurs and
the energy is zero.
Examples…
7.5 Quantum Mechanical Model