GENERAL CHEMISTRY PRINCIPLES AND MODERN APPLICATIONS ELEVENTH EDITION

Chemical Bonding I: Basic Concepts Slide 10 - 2 CONTENTS 10 -1 Lewis Theory:

10 -1 Lewis Theory: An Overview 1. Valence e− play a fundamental role in

Lewis Symbols and Lewis Structures A chemical symbol represents the nucleus and the core

Lewis structure Slide 10 - 5 General Chemistry: Chapter 10 Copyright © 2017 Pearson

Lewis Structures for Ionic Compounds No bond is 100% ionic. All bonds have some

10 -2 Covalent Bonding: An Introduction Slide 10 - 7 General Chemistry: Chapter 10

Coordinate Covalent Bonds (10. 5) (10. 6) Slide 10 - 8 General Chemistry: Chapter

FIGURE 10 -2 Formation of the ammonium ion, NH 4+ Slide 10 - 9

Multiple Covalent Bonds Slide 10 - 10 General Chemistry: Chapter 10 Copyright © 2017

Slide 10 - 11 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

FIGURE 10 -3 Paramagnetism of Oxygen Slide 10 - 12 General Chemistry: Chapter 10

10 -3 Polar Covalent Bonds and Electrostatic Potential Maps FIGURE 10 -4 Determination of

FIGURE 10 -5 The electrostatic potential maps for sodium chloride, hydrogen chloride and chlorine

Electronegativity (10. 10) (10. 11) Slide 10 - 15 General Chemistry: Chapter 10 Copyright

Slide 10 - 16 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

FIGURE 10 -6 Electronegativities of the elements Slide 10 - 17 General Chemistry: Chapter

FIGURE 10 -7 Percent ionic character of a chemical bond as a function of

Electrostatic potential maps demonstrating differences in ionic character. Slide 10 - 19 General Chemistry:

10 -4 Writing Lewis Structures • All the valence e– of atoms must appear

Skeletal Structure Identify central and terminal atoms. H H C H Slide 10 -

• Hydrogen atoms are always terminal atoms. • Central atoms are generally those

Summary scheme for drawing Lewis Structures FIGURE 10 -8 Summary scheme for drawing Lewis

Example 10 -7 Writing a Lewis Structure for a Polyatomic Ion NO 2+ e–

Formal Charge • • O • • FC(O) = 6 − 4 – 1

Formal Charge of an Alternative Lewis Structure O • • O—N—O • • FC(O–)

General Rules for Formal Charge • • Sum of FC is the overall charge.

10 -6 Exceptions to the Octet Rule Odd-Electron Species • • • N=O •

Incomplete Octets • • • • • • F • • F • •

Expanded Valence Shells • • expanded valence shell General Chemistry: Chapter 10 • •

Slide 10 - 32 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

10 -7 The Shapes of Molecules Bond length distance between nuclei. Bond angle between

Valence-Shell Electron Pair Repulsion (VSEPR) Theory Electron pairs repel each other whether they are

FIGURE 10 -11 Balloon analogy to valence-shell electron-pair repulsion Slide 10 - 35 General

FIGURE 10 -12 Molecular shapes based on tetrahedral electron-group geometry of CH 4, NH

Possibilities for Electron-Group Distributions Electron-group geometries • • • Slide 10 - 37 two

FIGURE 10 -13 Several electron-group geometries illustrated Slide 10 - 38 General Chemistry: Chapter

Slide 10 - 39 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

Slide 10 - 40 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

Applying VSEPR Theory 1. Draw a plausible Lewis structure. 2. Determine the number of

Structures with Multiple Covalent Bonds • • • • O • • General Chemistry:

Molecules with More Than One Central Atom The geometric distribution of terminal atoms around

Molecular Shapes and Dipole Moments FIGURE 10 -15 Polar molecules in an electric field

FIGURE 10 -16 Molecular shapes and dipole Moments Slide 10 - 45 General Chemistry:

10 -8 Bond Order and Bond Length Bond Order Single bond, bond order =

Slide 10 - 47 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

Average Bond Order • • General Chemistry: Chapter 10 • • (3) structures •

10 -9 Bond Energies FIGURE 10 -17 Some bond energies compared Slide 10 -

Slide 10 - 50 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

Calculating an Enthalpy of Reaction from Bond Energies. ΔHrxn = ΔH(bond breakage) + ΔH(bond

Predict whether a reaction will be endothermic or exothermic using bond energies. Slide 10

End of Chapter Slide 10 - 53 General Chemistry: Chapter 10 Copyright © 2017

Slides: 53

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GENERAL CHEMISTRY PRINCIPLES AND MODERN APPLICATIONS ELEVENTH EDITION PETRUCCI HERRING MADURA Chemical Bonding I: Basic Concepts BISSONNETTE 10 PHILIP DUTTON UNIVERSITY OF WINDSOR DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY Slide 10 - 1 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

Chemical Bonding I: Basic Concepts Slide 10 - 2 CONTENTS 10 -1 Lewis Theory: An Overview 10 -2 Covalent Bonding: An Introduction 10 -3 Polar Covalent Bonds and Electrostatic Potential Maps 10 -4 Writing Lewis Structures 10 -5 Resonance 10 -6 Exceptions to the Octet Rule 10 -7 Shapes of Molecules 10 -8 Bond Order and Bond Length 10 -9 Bond Energies General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

10 -1 Lewis Theory: An Overview 1. Valence e− play a fundamental role in chemical bonding. 2. e– transfer leads to ionic bonds. 3. Sharing of e– leads to a covalent bond. 4. e– are transferred or shared to give each atom a noble gas configuration, the octet. Gilbert Newton Lewis (1875 -1946) Slide 10 - 3 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

Lewis Symbols and Lewis Structures A chemical symbol represents the nucleus and the core e−. Dots around the symbol represent valence e−. • • Si • • • Al • • Slide 10 - 4 • As • • P • • • Se • • • Bi • • • Sb • • • • I • • • General Chemistry: Chapter 10 • • Ar • • • N • • • • Copyright © 2017 Pearson Canada Inc.

Lewis Structures for Ionic Compounds No bond is 100% ionic. All bonds have some covalent character. FIGURE 10 -1 Portion of an ionic crystal Slide 10 - 6 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

10 -3 Polar Covalent Bonds and Electrostatic Potential Maps FIGURE 10 -4 Determination of the electrostatic potential map for ammonia Slide 10 - 13 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

10 -4 Writing Lewis Structures • All the valence e– of atoms must appear in the structure. • Usually, all the e– are paired. • Usually, each atom requires an outer-shell octet of e–. • H only requires 2 e–. • Sometimes, multiple bonds may be needed. • Readily formed by C, N, O, S, and P. Slide 10 - 20 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

• Hydrogen atoms are always terminal atoms. • Central atoms are generally those with the lowest electronegativity. • Carbon atoms are always central atoms. • Generally structures are compact and symmetrical. Slide 10 - 22 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

Example 10 -7 Writing a Lewis Structure for a Polyatomic Ion NO 2+ e– = 5+6+6 -1=16 + O—N—O + • • • • Slide 10 - 24 • • O—N—O • • + • • O • • N General Chemistry: Chapter 10 • • O • • + • • • • O—N—O • • Copyright © 2017 Pearson Canada Inc.

Formal Charge • • O • • FC(O) = 6 − 4 – 1 (4) = 0 2 • • N • • O • • #bond pair e− + • • FC = 1 #valence e− −#lone pair e− − 2 FC(N) = 5− 0 – 1 (8) = +1 2 + • • O=N=O • • Slide 10 - 25 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

Formal Charge of an Alternative Lewis Structure O • • O—N—O • • FC(O–) = 6− 6 – + O • • O • • + 1 FC(N) = 5− 0 – (8) = +1 2 1 FC(O≡) = 6− 2 – (6) = +1 2 Slide 10 - 26 N • • + N 1 (2) =− 1 2 • • O • • - • • General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

General Rules for Formal Charge • • Sum of FC is the overall charge. FC should be as small as possible. Negative FC usually on most electronegative elements. FC of same sign on adjacent atoms is unlikely. + + • • Slide 10 - 27 • • O≡N—O • • - General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

Incomplete Octets • • • • • • F • • F • • F B • • F • • • • F B F – • • F • • F F • • – B • • F • • + • • F • • B B + - • • F F F • • • • Slide 10 - 30 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

Expanded Valence Shells • • expanded valence shell General Chemistry: Chapter 10 • • F • • • • • F • • F • • • Cl • • • • • S • • • F F • • Cl • • • Slide 10 - 31 • • • Cl P • • octet Cl • Cl • • Cl P • • Cl • • • • • expanded valence shell Copyright © 2017 Pearson Canada Inc.

10 -7 The Shapes of Molecules Bond length distance between nuclei. Bond angle between adjacent bonds. FIGURE 10 -10 Geometric shape of a molecule Slide 10 - 33 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

Valence-Shell Electron Pair Repulsion (VSEPR) Theory Electron pairs repel each other whether they are in chemical bonds (bond pairs) or unshared (lone pairs). Electron pairs assume orientations about an atom to minimize repulsions. Electron group geometry – distribution of e− pairs. Molecular geometry – distribution of nuclei. Slide 10 - 34 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

Possibilities for Electron-Group Distributions Electron-group geometries • • • Slide 10 - 37 two electron groups: linear three electron groups: trigonal planar four electron groups: tetrahedral five electron groups: trigonal bipyramidal six electron groups: octahedral General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

Applying VSEPR Theory 1. Draw a plausible Lewis structure. 2. Determine the number of e– groups and identify them as bond or lone pairs. 3. Establish the e– group geometry. 4. Determine the molecular geometry. Slide 10 - 41 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

Molecules with More Than One Central Atom The geometric distribution of terminal atoms around each central atom must be determined and the results then combined into a single description of the molecular shape. See Example 10 -12. Slide 10 - 43 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

10 -8 Bond Order and Bond Length Bond Order Single bond, bond order = 1 Double bond, bond order = 2 Triple bond, bond order = 3 Bond Length The distance between the centers of two atoms joined by a covalent bond. the length of the covalent bond between two atoms can be approximated as the sum of the covalent radii of the two atoms. Slide 10 - 46 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.

Average Bond Order • • General Chemistry: Chapter 10 • • (3) structures • • (1 + 2) bonds O = 4 3 O • - • • Slide 10 - 48 O - O • • average bond order = C C • • • O • • O O • - - - • • C • • O • • - • • O • = 1⅓ Copyright © 2017 Pearson Canada Inc.

Calculating an Enthalpy of Reaction from Bond Energies. ΔHrxn = ΔH(bond breakage) + ΔH(bond formation) ≈ BE(reactants) − BE(products) Slide 10 - 51 General Chemistry: Chapter 10 Copyright © 2017 Pearson Canada Inc.