Chemistry 8.3

1. Chemistry 8.3 8.3

2. 8.3 Molecular Orbitals • Molecular Orbitals • How are atomic and molecular orbitals related?

3. 8.3 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.

4. 8.3 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.

5. 8.3 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.

6. 8.3 Molecular Orbitals • A Sigma Bond

7. 8.3 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.

8. 8.3 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.

9. 8.3 Molecular Orbitals • Pi-bonding Molecular Orbital

10. 8.3 VSEPR Theory • VSEPR Theory • How does VSEPR theory help predict the shapes of molecules?

11. 8.3 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.

12. 8.3 VSEPR Theory • The valence-shell electron-pair repulsion theory, or VSEPR theory, explains the three-dimensional shape of methane.

13. 8.3 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.

14. 8.3 VSEPR Theory • The measured H—N—H bond angle is only 107°.

15. 8.3 VSEPR Theory • The measured bond angle in water is about 105°.

16. 8.3 VSEPR Theory • The carbon dioxide molecule is linear.

17. 8.3 VSEPR Theory • Nine Possible Molecular Shapes

18. 8.3 Hybrid Orbitals • Hybrid Orbitals • In what ways is orbital hybridization useful in describing molecules?

19. 8.3 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.

20. 8.3 Hybrid Orbitals • Hybridization Involving Single Bonds

21. 8.3 Hybrid Orbitals • Hybridization Involving Double Bonds

22. 8.3 Hybrid Orbitals • Hybridization Involving Triple Bonds

23. Hybrid Orbitals QUIZ TIME

24. 8.3 Section Quiz. • 1. A molecular orbital belongs to a • specific atom. • molecule as a whole. • specific pair of atoms. • central atom.

25. 8.3 Section Quiz. • 2. VSEPR theory enables prediction of 3-dimensional molecular shape because the valence electron pairs • are attracted to each other. • form molecules with only four possible shapes. • stay as far apart as possible. • always form tetrahedral shapes.

26. 8.3 Section Quiz. • 3. Orbital hybridization provides information about • both molecular bonding and molecular shape. • both molecular bonding and bond energy. • neither molecular bonding nor molecular shape. • neither molecular bonding nor bond energy.

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