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Chemistry 8.3 8.3 Slide 1 of 28 8.3 Bonding Theories This car is being painted by a process called electrostatic spray painting. The negatively charged droplets are attracted to the auto body. You will learn how attractive and repulsive forces influence the shapes of molecules. Slide 2 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > Molecular Orbitals Molecular Orbitals How are atomic and molecular orbitals related? Slide 3 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > Molecular Orbitals When two atoms combine, the molecular orbital model assumes that their atomic orbitals overlap to produce molecular orbitals, or orbitals that apply to the entire molecule. Slide 4 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > Molecular Orbitals Just as an atomic orbital belongs to a particular atom, a molecular orbital belongs to a molecule as a whole. A molecular orbital that can be occupied by two electrons of a covalent bond is called a bonding orbital. Slide 5 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > Molecular Orbitals Sigma Bonds When two atomic orbitals combine to form a molecular orbital that is symmetrical around the axis connecting two atomic nuclei, a sigma bond is formed. Slide 6 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > Molecular Orbitals A Sigma Bond Slide 7 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > Molecular Orbitals When two fluorine atoms combine, the p orbitals overlap to produce a bonding molecular orbital. The F—F bond is a sigma bond. Slide 8 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > Molecular Orbitals Pi Bonds In a pi bond (symbolized by the Greek letter ), the bonding electrons are most likely to be found in sausage-shaped regions above and below the bond axis of the bonded atoms. Slide 9 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > Molecular Orbitals Pi-bonding Molecular Orbital Slide 10 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > VSEPR Theory VSEPR Theory How does VSEPR theory help predict the shapes of molecules? Slide 11 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > VSEPR Theory The hydrogens in a methane molecule are at the four corners of a geometric solid. All of the H—C—H angles are 109.5°, the tetrahedral angle. Slide 12 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > VSEPR Theory The valence-shell electron-pair repulsion theory, or VSEPR theory, explains the threedimensional shape of methane. Slide 13 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > VSEPR Theory According to VSEPR theory, the repulsion between electron pairs causes molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible. Slide 14 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > VSEPR Theory The measured H—N—H bond angle is only 107°. Slide 15 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > VSEPR Theory The measured bond angle in water is about 105°. Slide 16 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > VSEPR Theory The carbon dioxide molecule is linear. Slide 17 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > VSEPR Theory Nine Possible Molecular Shapes Slide 18 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > Hybrid Orbitals Hybrid Orbitals In what ways is orbital hybridization useful in describing molecules? Slide 19 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > Hybrid Orbitals Orbital hybridization provides information about both molecular bonding and molecular shape. In hybridization, several atomic orbitals mix to form the same total number of equivalent hybrid orbitals. Slide 20 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > Hybrid Orbitals Hybridization Involving Single Bonds Slide 21 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > Hybrid Orbitals Hybridization Involving Double Bonds Slide 22 of 28 © Copyright Pearson Prentice Hall 8.3 Bonding Theories > Hybrid Orbitals Hybridization Involving Triple Bonds Slide 23 of 28 © Copyright Pearson Prentice Hall Bonding Theories > Hybrid Orbitals Simulation 7 Compare sp, sp2, and sp3 hybrid orbitals. Slide 24 of 28 © Copyright Pearson Prentice Hall 8.3 Section Quiz. Assess students’ understanding of the concepts in Section 8.3. Continue to: -or- Launch: Section Quiz Slide 25 of 28 © Copyright Pearson Prentice Hall 8.3 Section Quiz. 1. A molecular orbital belongs to a a. specific atom. b. molecule as a whole. c. specific pair of atoms. d. central atom. Slide 26 of 28 © Copyright Pearson Prentice Hall 8.3 Section Quiz. 2. VSEPR theory enables prediction of 3dimensional molecular shape because the valence electron pairs a. are attracted to each other. b. form molecules with only four possible shapes. c. stay as far apart as possible. d. always form tetrahedral shapes. Slide 27 of 28 © Copyright Pearson Prentice Hall 8.3 Section Quiz. 3. Orbital hybridization provides information about a. both molecular bonding and molecular shape. b. both molecular bonding and bond energy. c. neither molecular bonding nor molecular shape. d. neither molecular bonding nor bond energy. © Copyright Pearson Prentice Hall Slide 28 of 28 END OF SHOW