Slide 1 of 38 chemistry. © Copyright Pearson Prentice Hall Slide 2 of 38 Physics and the Quantum...

of 38

chemistry

© Copyright Pearson Prentice Hall

Slide 2 of 38

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.

5.3



>

Slide 3 of 38

Light

Light

How are the wavelength and frequency of light related?

5.3

of 38



> 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.

5.3

of 38



> 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).

5.3

of 38



> 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.

5.3

of 38



> Light

The product of the frequency and wavelength always equals a constant (c), the speed of light.

5.3

of 38



> 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, X-rays, and gamma rays. (add sketch slide 10)

• All electromagnetic waves travel in a vacuum at a speed of 2.998 108 m/s.

5.3

of 38



> 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.

5.3

of 38



> Light

The electromagnetic spectrum consists of radiation over a broad band of wavelengths. P 139.

5.3


Slide 11 of 38


> Light

Simulation 3

Explore the properties of electromagnetic radiation.


SAMPLE PROBLEM

Slide 12 of 38

5.1


SAMPLE PROBLEM

Slide 13 of 38

5.1


SAMPLE PROBLEM

Slide 14 of 38

5.1


SAMPLE PROBLEM

Slide 15 of 38

5.1


Slide 16 of 38

Practice Problems for Sample Problem 5.1

Problem-Solving 5.15 Solve Problem 15 with the help of an interactive guided tutorial.



>

Slide 17 of 38

Atomic Spectra

Atomic Spectra

What causes atomic emission spectra?

5.3


Slide 18 of 38


> 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.

5.3

of 38



> Atomic Spectra

A prism separates light into the colors it contains. When white light passes through a prism, it produces a rainbow of colors.

5.3

of 38



> Atomic Spectra

When light from a helium lamp passes through a prism, discrete lines are produced.

5.3

of 38



> Atomic Spectra

The frequencies of light emitted by an element separate into discrete lines to give the atomic emission spectrum of the element.

5.3

Mercury Nitrogen



>

Slide 22 of 38

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?

5.3

of 38



> 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

5.3


Slide 24 of 38



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.

5.3

of 38




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.

5.3


Slide 26 of 38



Animation 6

Learn about atomic emission spectra and how neon lights work.



>

Slide 27 of 38

Quantum Mechanics

Quantum Mechanics

How does quantum mechanics differ from classical mechanics?

5.3

of 38



> 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.

5.3

of 38



>

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.

of 38



>Wave-Particle Duality

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!

of 38



>

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

of 38



>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

of 38



> 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.

5.3


Slide 34 of 38


> Quantum Mechanics

Simulation 4

Simulate the photoelectric effect. Observe the results as a function of radiation frequency and intensity.


Slide 35 of 38


> 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.

5.3

of 38



>

Heisenberg Uncertainty Principle

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!

“One cannot simultaneously determine both the position and momentum of an electron.”

Werner Heisenberg


Slide 37 of 38


> Quantum Mechanics

The Heisenberg Uncertainty Principle

5.3

of 38



> 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 ordinary-sized object such as cars or airplanes.

5.3


Slide 39 of 38


>


Slide 40 of 38


>It is more obvious with 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 41 of 38

Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

5.3 Section Quiz.

5.3.


Slide 42 of 38

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 43 of 38

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.


Slide 44 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 45 of 38

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 46 of 38


> Concept Map 5

Concept Map 5 Solve the concept map with the help of an interactive guided tutorial.

END OF SHOW

Slide 1 of 38 chemistry. © Copyright Pearson Prentice Hall Slide 2 of 38 Physics and the Quantum...

Documents

Transcript of Slide 1 of 38 chemistry. © Copyright Pearson Prentice Hall Slide 2 of 38 Physics and the Quantum...