Bài giảng Chapter 7 The Quantum-Mechanical Model of the Atom

Chemistry, Julia Burdge, 2st Ed.
McGraw Hill.

Chapter 7
The QuantumMechanical
Model of the
Atom
Mr. Truong Minh Chien ;
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2011, NKMB Co., Ltd.


The Behavior of the Very Small
• electrons are incredibly small
a single speck of dust has more electrons than the
number of people who have ever lived on earth

• electron behavior determines much of the

behavior of atoms
• directly observing electrons in the atom is
impossible, the electron is so small that
observing it changes its behavior
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A Theory that Explains Electron Behavior
• the quantum-mechanical model explains the manner
•

electrons exist and behave in atoms
helps us understand and predict the properties of atoms
that are directly related to the behavior of the electrons
 why some elements are metals while others are nonmetals
 why some elements gain 1 electron when forming an anion,
while others gain 2
 why some elements are very reactive while others are
practically inert
 and other Periodic patterns we see in the properties of the
elements

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The Nature of Light
its Wave Nature
• light is a form of electromagnetic radiation
 composed of perpendicular oscillating waves, one for the
electric field and one for the magnetic field
 an electric field is a region where an electrically charged particle
experiences a force
 a magnetic field is a region where an magnetized particle experiences
a force

• all electromagnetic waves move through space at the
same, constant speed
 3.00 x 108 m/s in a vacuum = the speed of light, c

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Speed of Energy Transmission

Chemistry, Julia Burdge, 2nd e., McGraw Hill.

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Electromagnetic Radiation

Chemistry, Julia Burdge, 2nd e., McGraw Hill.

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Characterizing Waves
• the amplitude is the height of the wave
the distance from node to crest
or node to trough

the amplitude is a measure of how intense the light
is – the larger the amplitude, the brighter the light

• the wavelength, () is a measure of the distance
covered by the wave

the distance from one crest to the next
or the distance from one trough to the next, or the
distance between alternate nodes
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Wave Characteristics

Chemistry, Julia Burdge, 2nd e., McGraw Hill.

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Wave animation

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Characterizing Waves
• the frequency, () is the number of waves that
pass a point in a given period of time

the number of waves = number of cycles
units are hertz, (Hz) or cycles/s = s-1
1 Hz = 1 s-1

• the total energy is proportional to the amplitude
and frequency of the waves

the larger the wave amplitude, the more force it has
the more frequently the waves strike, the more total
force there is
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The Relationship Between
Wavelength and Frequency

• for waves traveling at the same speed, the shorter
the wavelength, the more frequently they pass
• this means that the wavelength and frequency of
electromagnetic waves are inversely proportional
since the speed of light is constant, if we know
wavelength we can find the frequency, and visa versa



 s  
  m
-1

Tro, Chemistry: A Molecular Approach

c

m
s

11


Example 7.1- Calculate the wavelength of red
light with a frequency of 4.62 x 10 14 s-1
Given:  = 4.62 x 1014 s-1
Find: , (nm)
Concept Plan: s-1)
 (m)
c



1 nm

 (nm)

10  9 m

Relationships: ∙ = c, 1 nm = 10-9 m
Solve:
c 3.00 108 m  s -1
7
 

6

.
49

10
m
14
1

4.62 10 s
1 nm
7
6.49 10 m   9 6.49 102 nm
10 m
Check: the unit is correct, the wavelength is appropriate
for red light
Chemistry, Julia Burdge, 2nd e., McGraw Hill.

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Practice – Calculate the wavelength of a radio
signal with a frequency of 100.7 MHz

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Practice – Calculate the wavelength of a radio
signal with a frequency of 100.7 MHz

Given:  = 100.7 MHz
Find: , (m)
Concept Plan: Hz)
6 -1

10 s
1 MHz

 (s-1)

c



 (m)

Relationships: ∙ = c, 1 MHz = 106 s-1
Solve:
106 s -1
100.7 MHz 
1.007 108 s -1
1 MHz
c 3.00 108 m  s -1
 
2.98 m
8
1

1.007 10 s
Check: the unit is correct, the wavelength is appropriate

for radiowaves
Chemistry, Julia Burdge, 2nd e., McGraw Hill.

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Color
• the color of light is determined by its wavelength
 or frequency

• white light is a mixture of all the colors of visible light
 a spectrum
 RedOrangeYellowGreenBlueViolet

• when an object absorbs some of the wavelengths of
white light while reflecting others, it appears colored
 the observed color is predominantly the colors reflected

Chemistry, Julia Burdge, 2nd e., McGraw Hill.

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Amplitude & Wavelength

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Electromagnetic Spectrum

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Continuous Spectrum

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The Electromagnetic Spectrum
• visible light comprises only a small fraction of
all the wavelengths of light – called the
electromagnetic spectrum
• short wavelength (high frequency) light has
high energy
radiowave light has the lowest energy
gamma ray light has the highest energy

• high energy electromagnetic radiation can
potentially damage biological molecules
ionizing radiation
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Thermal Imaging using Infrared Light

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