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© Copyright Pearson Prentice Hall

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START NOTES SECTION 4.2

Please add quiz answers to notes; they were accidentally left off for a place to record. Watch all video links carefully.

Copyright © by Holt, Rinehart and Winston. All rights reserved.

ResourcesChapter menu

Visual Concepts

Click below to watch the Visual Concept.

Visual Concept

Avogadro’s Number

Chapter 3

http://my.hrw.com/sh/hc6_003036809x/student/ch03/sec03/vc05/hc603_03_v05fs.htm

WATCH THIS VIDEO TO CONNECT BACK WITH THE M&M & MOLE MINI-LAB






Section 2 The Quantum Model of the Atom

Lesson Starter

• Write down your address using the format of street name, house/apartment number, and ZIP Code.

• These items describe the location of your residence.

• How many students have the same ZIP Code? How many live on the same street? How many have the same house number?

Chapter 4




Lesson Starter, continued

• In the same way that no two houses have the same address, no two electrons in an atom have the same set of four quantum numbers.

• In this section, you will learn how to use the quantum-number code to describe the properties of electrons in atoms.

Chapter 4




Objectives

• Discuss Louis de Broglie’s role in the development of the quantum model of the atom.

• Compare and contrast the Bohr model and the quantum model of the atom.

• Explain how the Heisenberg uncertainty principle and the Schrödinger wave equation led to the idea of atomic orbitals.

Chapter 4




Objectives, continued

• List the four quantum numbers and describe their significance.

• Relate the number of sublevels corresponding to each of an atom’s main energy levels, the number of orbitals per sublevel, and the number of orbitals per main energy level.

Chapter 4




Electrons as Waves

• French scientist Louis de Broglie suggested that electrons be considered waves confined to the space around an atomic nucleus.

• It followed that the electron waves could exist only at specific frequencies.

• According to the relationship E = hv, these frequencies corresponded to specific energies—the quantized energies of Bohr’s orbits.

Chapter 4




Electrons as Waves, continued

• Electrons, like light waves, can be bent, or diffracted.

• Diffraction refers to the bending of a wave as it passes by the edge of an object or through a small opening.

• Electron beams, like waves, can interfere with each other.

• Interference occurs when waves overlap.

Chapter 4



Visual Concepts


Visual Concept

De Broglie and the Wave-Particle Nature of Electrons

Chapter 4





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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.

4.2




The Heisenberg Uncertainty Principle

• German physicist Werner Heisenberg proposed that any attempt to locate a specific electron with a photon knocks the electron off its course.

Chapter 4

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> 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.

4.2



Visual Concepts


Visual Concept

Heisenberg Uncertainty Principle

Chapter 4






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> Quantum Mechanics

The Heisenberg Uncertainty Principle

4.2




The Schrödinger Wave Equation

• In 1926, Austrian physicist Erwin Schrödinger developed an equation that treated electrons in atoms as waves.

• Together with the Heisenberg uncertainty principle, the Schrödinger wave equation laid the foundation for modern quantum theory.

• Quantum theory describes mathematically the wave properties of electrons and other very small particles.

Chapter 4



Visual Concepts


Visual Concept

Electron Cloud

Chapter 4








The Schrödinger Wave Equation, continued

• Electrons do not travel around the nucleus in neat orbits, as Bohr had postulated.

• Instead, they exist in certain regions called orbitals.

• An orbital is a three-dimensional region around the nucleus that indicates the probable location of an electron.

Chapter 4




Atomic Orbitals and Quantum Numbers

• Quantum numbers specify the properties of atomic orbitals and the properties of electrons in orbitals.

• The principal quantum number, symbolized by n, indicates the main energy level occupied by the electron. 1, 2, 3, etc. as n increases the electron’s energy level and its distance from the nucleus increases.

• The angular momentum quantum number, symbolized by l, indicates the shape of the orbital.

Chapter 4

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Models of the Atom > Atomic Orbitals

Different atomic orbitals are denoted by letters. The s orbitals are spherical, and p orbitals are dumbbell-shaped.

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Four of the five d orbitals have the same shape but different orientations in space.

f orbitals are more complex in nature as well.

There are seven f-orbitals.

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An atomic orbital is often thought of as a region of space in which there is a high probability of finding an electron.

Each energy sublevel corresponds to an orbital of a different shape, which describes where the electron is likely to be found.

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The numbers and kinds of atomic orbitals depend on the energy sublevel.

4.2

The number of orbitals in each the first 4 main energy levels equals n2.

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The number of electrons allowed in each of the first four energy levels are shown here.

4.2

The maximum number of electrons in each

of the energy levels is equal to 2n2.




Atomic Orbitals and Quantum Numbers, continued• The magnetic quantum number, symbolized by

m, indicates the orientation of an orbital around the nucleus & can be an integer from - l to + l where l is the angular momentum. (This is a little “L” notation)

• The spin quantum number has only two possible values—(+1/2 , −1/2)—which indicate the two fundamental spin states of an electron in an orbital.

• A single orbital can hold a maximum of 2 electrons which must have opposite spin states.

Chapter 4



Visual Concepts


Visual Concept

Quantum Numbers and Orbitals

Chapter 4







Shapes of s, p, and d Orbitals

Section 2 The Quantum Model of the AtomChapter 4



Electrons Accommodated in Energy Levels and Sublevels




Quantum Numbers of the First 30 Atomic Orbitals



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Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

5.3 Section Quiz.

5.3.


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Online Self-Check Quiz

Complete the online Quiz and record answers. Ask if you have any questions about your answers.

click here for online Quiz 4.2

(10 questions)

You must be in the “Play mode” for the slideshow for hyperlink to work.

http://my.hrw.com/sh/hc6_003036809x/student/ch04/sec02/hc604_02sq.htm


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VIDEOS FOR ADDITIONAL INSTRUCTION

Additional Videos for Section 4.2: The Quantum Model of the Atom•Atomic Orbitals (4:27)•Quantum Numbers (3:12)•Orbital Diagrams (4:58)

http://brightstorm.com/science/chemistry/the-atom/atomic-orbitals

http://brightstorm.com/science/chemistry/the-atom/quantum-numbers

© copyright pearson prentice hall slide of 27 end show division page start notes section 4.2 please...

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