Bonding Part 1 Lewis Structures - Full Lecture Slides PDF

Chapter Outline (1 of 2) 9.1 Bonding Models and AIDS Drugs 9.2 Types of Chemical Bonds 9.3 Representing Valence Electrons with Dots 9.4 Lewis Structures: An Introduction to Ionic and Covalent Bonding 9.5 The Ionic Bonding Model 9.6 Covalent Bond Energies, Lengths, and Vibrations. 9.7 Electronega...

Chapter Outline (1 of 2) 9.1 Bonding Models and AIDS Drugs 9.2 Types of Chemical Bonds 9.3 Representing Valence Electrons with Dots 9.4 Lewis Structures: An Introduction to Ionic and Covalent Bonding 9.5 The Ionic Bonding Model 9.6 Covalent Bond Energies, Lengths, and Vibrations. 9.7 Electronegativity and Bond Polarity (towards the end) 9.8 Resonance and Formal Charge Copyright © 2023 Pearson Canada Inc. 9-1 Chapter Outline (2 of 2) 9.9 Exceptions to the Octet Rule: Drawing Lewis Structures for Odd-Electron Species and Incomplete Octets 9.10 Lewis Structures for Hypercoordinate Compounds Copyright © 2023 Pearson Canada Inc. 9-2 9.2 Types of Chemical Bonds Types of Atoms Type of Bond Characteristic of Bond Metal and nonmetal Ionic Electrons transferred Nonmetal and nonmetal Covalent Electrons shared Metal and metal Metallic Electrons pooled Copyright © 2023 Pearson Canada Inc. 9-3 Ionic, Covalent and Metallic Bonding Chemical bonds form because they lower the potential energy between the charged particles that compose atoms. neither atom transfers electrons to the other. Instead, the two atoms share some metal atom electrons. The becomes a shared electrons cation and the interact with the nonmetal nuclei of both of the atom an bonding atoms anion. These metallic bonding—electron oppositely sea model—all of the atoms in charged ions then attract a metal lattice pool their one another, valence electrons. lowering their Delocalized throughout the overall entire metal. potential The positively charged metal energy as atoms are then attracted to described by the sea of electrons, holding Coulomb’s law the metal together. Figure 9.1 Ionic, Covalent, and Metallic Bonding [top left: Madlen/Shutterstock; top right: Valentyn Volkov/123RF; bottom: Tim Ridley/DK Images] Copyright © 2023 Pearson Canada Inc. 9-4 9.2 Representing Valence Electrons with Dots 2s1 2s 2 2s 2 2p1 2s 2 2p 2 2s 2 2p3 2s 2 2p 4 2s 2 2p5 2s 2 2p6 Copyright © 2023 Pearson Canada Inc. 9-5 Summarizing the Method for Drawing Lewis Structures 1. Calculate the total number of electrons for the Lewis structure by summing the valence electrons of each atom in the molecule. 2. Write the correct skeletal structure for the molecule, drawing a bond between each set of bonding atoms. 3. Distribute the remaining unaccounted-for electrons in pairs among the atoms, giving octets (except for hydrogen) to as many atoms as possible. 4. If any nonhydrogen atoms lack an octet, form double or triple bonds, as necessary, to give them octets. Copyright © 2023 Pearson Canada Inc. 9-6 9.4 Lewis Structures: An Introduction to Ionic and Covalent Bonding total of 8 valence e− 4 valence e− used in bonds 4 valence e− used in lone pairs correct Lewis structure Copyright © 2023 Pearson Canada Inc. 9-7 Example Draw the Lewis structure for CO2. Carbon is the central atom. Repeat the process for NH2Cl (Hint: The skeletal structure is similar to that of NH3 with Cl replacing an H.) - O2 - CH2O (carbon central) - N2 - HCN (carbon central) Copyright © 2023 Pearson Canada Inc. 9-8 Drawing Lewis Structures for Molecular Compounds (1 of 4) Copyright © 2023 Pearson Canada Inc. 9-9 Drawing Lewis Structures for Molecular Compounds (2 of 4) Copyright © 2023 Pearson Canada Inc. 9 - 10 Drawing Lewis Structures for Molecular Compounds (3 of 4) 12 e– 2 e– 12 e– satisfy octets each oxygen atom has an octet Copyright © 2023 Pearson Canada Inc. 9 - 11 Drawing Lewis Structures for Molecular Compounds (4 of 4) 10 e– 0 e– 2 e– 10 e– satisfy octets each nitrogen atom has an octet Copyright © 2023 Pearson Canada Inc. 9 - 12 Hydronium Ion 9 e– available 6 e– for bonding octet violated oxygen has 3 e– left over lose e– an octet create +ve charge Copyright © 2023 Pearson Canada Inc. 9 - 13 Writing Lewis Structures for Polyatomic Ions Follow the same procedure for drawing Lewis structures, but when counting electrons in the first step: Add one electron for each unit of negative charge on the ion. Remove one electron for each unit of positive charge on the ion. Copyright © 2023 Pearson Canada Inc. 9 - 14 Example Draw the Lewis structure for ClO-. Repeat for NH4+ H3O+ Copyright © 2023 Pearson Canada Inc. 9 - 15 Ionic Bonding and Electron Transfer The Lewis structure of an anion is usually written within brackets with the charge in the upper right-hand corner, outside the brackets. The positive and negative charges attract one another, resulting in the compound KCl. Copyright © 2023 Pearson Canada Inc. 9 - 16 Example Draw the Lewis structure for CaF2. Repeat for AgBr Copyright © 2023 Pearson Canada Inc. 9 - 17 Resonance and Formal Charge In some molecules, you can write more than one valid Lewis structure. In cases such as this—where there are two or more valid Lewis structures for the same molecule—we find that in nature, the molecule exists as an average of the two Lewis structures. Called resonance structures, with a double-headed arrow between them: O3 valence e – = 3  6 = 18 Copyright © 2023 Pearson Canada Inc. 9 - 18 Copyright © 2023 Pearson Canada Inc. 9 - 19 Example Write a valid Lewis structure for the NO3− ion Copyright © 2023 Pearson Canada Inc. 9 - 20 Bond Order The number of bonding pairs of electrons between two atoms. In a covalent bond between two atoms, a single bond has a bond order of one, a double bond has a bond order of two, a triple bond has a bond order of three, and so on. The higher the bond order, the higher the molecular stability. 1. Draw the Lewis structure. 2. Count the total number of bonds. 3. Count the number of bond groups between individual atoms. 4. Divide the number of bonds between atoms by the total number of bond groups in the molecule. Copyright © 2023 Pearson Canada Inc. 9 - 21 Example Calculate bond order in NO3− Copyright © 2023 Pearson Canada Inc. 9 - 22 Formal Charge (1 of 2) Formal charge is the charge if all bonding electrons were shared equally between bonding atoms. FC = Valence e − – ( Nonbond ing e − + ½ Bonding e − ) Copyright © 2023 Pearson Canada Inc. 9 - 23 Formal Charge (2 of 2) The sum of the formal charges in molecules or ions must equal the overall charge of the ion or molecule. 1. Smaller formal charges on individual atoms are better than larger ones. 2. When formal charges cannot be avoided, negative formal charges reside on the most electronegative atom. Copyright © 2023 Pearson Canada Inc. 9 - 24 Example Assign formal charges to each atom in the resonance structures for methanoic acid (or formic acid), HCOOH. Which resonance form is likely to contribute the most to the correct structure of methanoic acid? Copyright © 2023 Pearson Canada Inc. 9 - 25