chapter05_section03.pps

(1)

Slide 1 of 38

(2)

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.

(3)

Physics and the Quantum Mechanical Model >

Slide 3 of 38

Light

Light

How are the wavelength and frequency of light related?

(4)

Slide 4 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)

Slide 5 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).

(6)

Slide 6 of 38

Light

The wavelength and frequency of light are inversely proportional to each other.

(7)

Slide 7 of 38

Light

The product of the frequency and

wavelength always equals a constant (c), the speed of light.

(8)

Slide 8 of 38

Light

According to the wave model, light consists of electromagnetic waves.

•

Electromagnetic radiation includes radio waves, microwaves, infrared waves, visible light, ultraviolet waves, X-rays, and gamma rays.

•

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

(9)

Slide 9 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.

(10)

Slide 10 of 38

Light

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

(11)

Slide 11 of 38

Light

Simulation 3

(12)

SAMPLE PROBLEM

Slide 12 of 38

(13)

SAMPLE PROBLEM

Slide 13 of 38

(14)

SAMPLE PROBLEM

Slide 14 of 38

(15)

SAMPLE PROBLEM

Slide 15 of 38

(16)

Slide 16 of 38

Practice Problems for Sample Problem 5.1

(17)

Slide 17 of 38

Atomic Spectra

Atomic Spectra

What causes atomic emission spectra?

(18)

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.

(19)

Slide 19 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.

(20)

Slide 20 of 38

Atomic Spectra

When light from a helium lamp passes

through a prism, discrete lines are produced.

(21)

Slide 21 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

(22)

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?

(23)

Slide 23 of 38

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.

(24)

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.

(25)

Slide 25 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.

(26)

Slide 26 of 38

Animation 6

(27)

Slide 27 of 38

Quantum Mechanics

Quantum Mechanics

How does quantum mechanics differ from classical mechanics?

(28)

Slide 28 of 38

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.

(29)

Slide 29 of 38

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.

(30)

Slide 30 of 38

Simulation 4

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

(31)

Slide 31 of 38

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.

(32)

Slide 32 of 38

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.

(33)

Slide 33 of 38

The Heisenberg Uncertainty Principle

(34)

Slide 34 of 38

Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

5.3 Section Quiz.

(35)

Slide 35 of 38

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

(36)

Slide 36 of 38

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.

(37)

Slide 37 of 38

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.

(38)

Slide 38 of 38

Concept Map 5

Concept Map 5 Solve the

(39)