Physics and the Quantum Mechanical Model

download report

Transcript Physics and the Quantum Mechanical Model

chemistry
Slide
1 of 38
5.3
Physics and the Quantum Mechanical
Model
Neon advertising signs are
formed from glass tubes bent in
various shapes. An electric
current passing through the gas
in each glass tube makes the
gas glow with its own
characteristic color. You will
learn why each gas glows with a
specific color of light.
Slide
2 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Light
Light
How are the wavelength and frequency
of light related?
Slide
3 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Light
• The amplitude of a wave is the wave’s height
from zero to the crest.
• The wavelength, represented by  (the Greek
letter lambda), is the distance between the
crests.
Slide
4 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Light
• The frequency, represented by  (the Greek
letter nu), is the number of wave cycles to
pass a given point per unit of time.
• The SI unit of cycles per second is called a
hertz (Hz).
Slide
5 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Light
The wavelength and frequency of light are
inversely proportional to each other.
As wavelength (λ) increases, frequency decreases.
As wavelength (λ) decreases, frequency increases.
increases.
Slide
6 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Light
The product of the frequency and wavelength
always equals a constant (c), the speed of light.
Slide
7 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Light
According to the wave model, light consists of
electromagnetic waves.
• Electromagnetic radiation includes radio
waves, radar, microwaves, infrared waves,
visible light (ROY G BIV), ultraviolet waves, Xrays, and gamma rays. (add sketch slide 10)
• All electromagnetic waves travel in a vacuum
at a speed of 2.998  108 m/s.
Slide
8 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Light
Sunlight consists of light with a continuous range
of wavelengths and frequencies.
• When sunlight passes through a prism, the
different frequencies separate into a
spectrum of colors.
• In the visible spectrum, red light has the
longest wavelength and the lowest frequency.
Slide
9 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Light
The electromagnetic spectrum consists of radiation over
a broad band of wavelengths. P 139.
Slide
10 of 38
© Copyright Pearson Prentice Hall
Physics and the Quantum
Mechanical Model
>
Light
Simulation 3
Explore the properties of electromagnetic
radiation.
Slide
11 of 38
© Copyright Pearson Prentice Hall
SAMPLE PROBLEM 5.1
Slide
12 of 38
© Copyright Pearson Prentice Hall
SAMPLE PROBLEM 5.1
Slide
13 of 38
© Copyright Pearson Prentice Hall
SAMPLE PROBLEM 5.1
Slide
14 of 38
© Copyright Pearson Prentice Hall
SAMPLE PROBLEM 5.1
Slide
15 of 38
© Copyright Pearson Prentice Hall
Practice Problems for Sample Problem 5.1
Problem-Solving 5.15 Solve
Problem 15 with the help of an
interactive guided tutorial.
Slide
16 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Atomic Spectra
Atomic Spectra
What causes atomic emission spectra?
Slide
17 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Atomic Spectra
When atoms absorb energy, electrons
move into higher energy levels. These
electrons then lose energy by emitting
light when they return to lower energy
levels.
Slide
18 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Atomic Spectra
A prism separates light into the colors it contains.
When white light passes through a prism, it
produces a rainbow of colors.
Slide
19 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Atomic Spectra
When light from a helium lamp passes through a
prism, discrete lines are produced.
Slide
20 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Atomic Spectra
The frequencies of light emitted by an
element separate into discrete lines to give
the atomic emission spectrum of the
element.
Mercury
Nitrogen
Slide
21 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
An Explanation of Atomic Spectra
An Explanation of Atomic Spectra
How are the frequencies of light an atom
emits related to changes of electron
energies?
Slide
22 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
An Explanation of Atomic Spectra
In the Bohr model, the lone electron in the hydrogen
atom can have only certain specific energies.
• When the electron has its lowest possible
energy, the atom is in its ground state.
• Excitation of the electron by absorbing energy
raises the atom from the ground state to an
excited state.
• A quantum of energy in the form of light is
emitted when the electron drops back to a lower
energy level. See p. 143, figure 5.14
Slide
23 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
An Explanation of Atomic Spectra
The light emitted by an electron moving
from a higher to a lower energy level has
a frequency directly proportional to the
energy change of the electron.
Slide
24 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
An Explanation of Atomic Spectra
The three groups of lines in the hydrogen
spectrum correspond to the transition of
electrons from higher energy levels to lower
energy levels. See p. 143.
Slide
25 of 38
© Copyright Pearson Prentice Hall
Physics and the Quantum
Mechanical Model
>
An Explanation of Atomic Spectra
Animation 6
Learn about atomic emission spectra and how
neon lights work.
Slide
26 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Quantum Mechanics
Quantum Mechanics
How does quantum mechanics differ
from classical mechanics?
Slide
27 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Quantum Mechanics
In 1905, Albert Einstein successfully explained
experimental data by proposing that light could
be described as quanta of energy.
• The quanta behave as if they were particles.
• Light quanta are called photons.
In 1924, De Broglie developed an equation that
predicts that all moving objects have wavelike
behavior.
Slide
28 of 38
© Copyright Pearson Prentice Hall
Physics and the Quantum
Mechanical Model
What is light?
>
Light is a particle - it comes in chunks.
Light is a wave - we can measure its
wavelength and it behaves as a wave
If we combine E=mc2 , c=f, E = 1/2 mv2 and E
= hf, then we can get:
 = h/mv
(from Louis de Broglie)
called de Broglie’s equation
Calculates the wavelength of a particle.
Slide
29 of 38
© Copyright Pearson Prentice Hall
Physics and the Quantum
Wave-Particle
Duality Model
Mechanical
>
J.J. Thomson won the Nobel prize for describing the
electron as a particle.
His son, George Thomson won the Nobel prize for
describing the wave-like nature of the electron.
The
electron is
a particle!
The electron
is an energy
wave!
Slide
30 of 38
© Copyright Pearson Prentice Hall
Physics and the Quantum
Mechanical Model
>
Confused? You’ve Got Company!
“No familiar conceptions can be
woven around the electron;
something unknown is doing we
don’t know what.”
Physicist Sir Arthur Eddington
The Nature of the Physical World
1934
Slide
31 of 38
© Copyright Pearson Prentice Hall
Physics and the Quantum
Mechanical Model
The physics of the very small
>
Quantum mechanics explains how very
small particles behave
• Quantum mechanics is an explanation
for subatomic particles and atoms as
waves
Classical mechanics describes the
motions of bodies much larger than
atoms
Slide
32 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Quantum Mechanics
Today, the wavelike properties of beams of
electrons are useful in magnifying objects. The
electrons in an electron microscope have much
smaller wavelengths than visible light. This
allows a much clearer enlarged image of a very
small object, such as this mite.
Slide
33 of 38
© Copyright Pearson Prentice Hall
Physics and the Quantum
Mechanical Model
>
Quantum Mechanics
Simulation 4
Simulate the photoelectric effect. Observe the
results as a function of radiation frequency
and intensity.
Slide
34 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Quantum Mechanics
Classical mechanics adequately
describes the motions of bodies much
larger than atoms, while quantum
mechanics describes the motions of
subatomic particles and atoms as waves.
Slide
35 of 38
© Copyright Pearson Prentice Hall
Physics and the Quantum
Mechanical Model
>
Heisenberg Uncertainty
Principle
“One cannot simultaneously
determine both the position
and momentum of an
electron.”
Werner Heisenberg
You can find out where the
electron is, but not where it is
going.
OR…
You can find out where the
electron is going, but not where
it is!
© Copyright Pearson Prentice Hall
Slide
36 of 38
5.3
Physics and the Quantum
Mechanical Model
>
Quantum Mechanics
The Heisenberg Uncertainty Principle
Slide
37 of 38
© Copyright Pearson Prentice Hall
5.3
Physics and the Quantum
Mechanical Model
>
Quantum Mechanics
The Heisenberg uncertainty principle states
that it is impossible to know exactly both the
velocity and the position of a particle at the same
time.
• This limitation is critical in dealing with small
particles such as electrons.
• This limitation does not matter for ordinarysized object such as cars or airplanes.
Slide
38 of 38
© Copyright Pearson Prentice Hall
Physics and the Quantum
Mechanical Model
>
Slide
39 of 38
© Copyright Pearson Prentice Hall
Physics and the Quantum >
Mechanical
It is more obvious
withModel
the very small objects
To measure where a electron is, we use
light.
But the light energy moves the electron
And hitting the electron changes the
frequency of the light.
Slide
40 of 38
© Copyright Pearson Prentice Hall
5.3 Section Quiz.
Assess students’ understanding
of the concepts in Section 5.3.
Continue to:
-or-
Launch:
Section Quiz
Slide
41 of 38
© Copyright Pearson Prentice Hall
5.3 Section Quiz.
1. Calculate the frequency of a radar wave with
a wavelength of 125 mm.
a. 2.40 109 Hz
b. 2.40 1024 Hz
c. 2.40 106 Hz
d. 2.40 102 Hz
Slide
42 of 38
© Copyright Pearson Prentice Hall
5.3 Section Quiz.
2. The lines in the emission spectrum for an
element are caused by
a. the movement of electrons from lower to
higher energy levels.
b. the movement of electrons from higher to
lower energy levels.
c. the electron configuration in the ground
state.
d. the electron configuration of an atom.
© Copyright Pearson Prentice Hall
Slide
43 of 38
5.3 Section Quiz.
3. Spectral lines in a series become closer
together as n increases because the
a. energy levels have similar values.
b. energy levels become farther apart.
c. atom is approaching ground state.
d. electrons are being emitted at a slower
rate.
Slide
44 of 38
© Copyright Pearson Prentice Hall
www.chembored.com
Chem 12
Quantum mechanics: the sequel
Overlapping shells slide: slide 9 (this is the 2nd
day of the quantum mechanics lesson).
Slide
45 of 38
© Copyright Pearson Prentice Hall
Physics and the Quantum
Mechanical Model
>
Concept Map 5
Concept Map 5 Solve the
concept map with the help of an
interactive guided tutorial.
© Copyright Pearson Prentice Hall
Slide
46 of 38
END OF SHOW