PHILIP DUTTON UNIVERSITY OF WINDSOR DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY

1. GENERAL CHEMISTRY Principles and Modern Applications TENTH EDITION PETRUCCI HERRING MADURA BISSONNETTE 10 Chemical Bonding I:Basic Concepts PHILIP DUTTON UNIVERSITY OF WINDSOR DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY General Chemistry: Chapter 10

2. Chemical Bonding I:Basic Concepts General Chemistry: Chapter 10

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

4. •• •• •• •• •• As Bi P Sb N • • • • • • • • • • • • • • • •• •• •• Al Ar • Se •• I • •• • • •• • • •• • •• Lewis Symbols and Lewis Structures • Si • • • A chemical symbol represents the nucleus and the coree-. Dots around the symbol represent valence e-. General Chemistry: Chapter 10

5. Lewis structure General Chemistry: Chapter 10

8. 10-2 Covalent Bonding: An Introduction General Chemistry: Chapter 10

9. + H H - •• N H Cl •• •• H N H •• •• H H Coordinate Covalent Bonds Cl H FIGURE 10-2 • Formation of the ammonium ion, NH4+ General Chemistry: Chapter 10

10. • • • •• •• C O O •• •• • •• •• • • • •• •• C O O C O O •• •• •• •• • Multiple Covalent Bonds • • • O C O • • • • • • • • • • • • • General Chemistry: Chapter 10

11. • • N N •• •• • • • N N N N •• •• •• •• • Multiple Covalent Bonds • • •• N N •• • • • • General Chemistry: Chapter 10

12. Paramagnetism of Oxygen General Chemistry: Chapter 10

14. 10-3 Polar Covalent Bonds and Electrostatic Potential Maps FIGURE 10-4 • Determination of the electrostatic potential map for ammonia General Chemistry: Chapter 10

15. FIGURE 10-5 The electrostatic potential maps for sodium chloride, hydrogen chloride and chlorine General Chemistry: Chapter 10

16. Electronegativity FIGURE 10-6 • Electronegativities of the elements General Chemistry: Chapter 10

17. FIGURE 10-7 Percent ionic character of a chemical bond as a function of electronegativity difference General Chemistry: Chapter 10

20. 10-4 Writing Lewis Structures • All the valence e- of atoms must appear. • Usually, the e- are paired. • Usually, each atom requires an octet. • H only requires 2 e-. • Multiple bonds may be needed. • Readily formed by C, N, O, S, and P. General Chemistry: Chapter 10

21. Skeletal Structure H H H C C O H H H Identify central and terminal atoms. General Chemistry: Chapter 10

22. Skeletal Structure • 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. General Chemistry: Chapter 10

23. FIGURE 10-8 Summary scheme for drawing Lewis Structures General Chemistry: Chapter 10

24. •• •• O=N=O •• •• 1 FC(O) = 6 - 4 – (4) = 0 2 1 FC(N) = 5 - 0 – (8) = +1 2 Formal Charge The formal charge on an atom in a Lewis structure is the number of valence e- in the free atom minus the number of e- assigned to that atom in the Lewis structure. 1 FC = #valence e- - #lone pair e- - #bond pair e- + 2 General Chemistry: Chapter 10

25. Formal Charge of an Alternative Lewis Structure •• •• •• O N O •• 1 FC(O≡) = 6 - 2 – (6) = +1 2 1 FC(O—) = 6 - 6 – (2) = -1 2 1 FC(N) = 5 - 0 – (8) = +1 2 + - + •• •• O—N—O •• •• •• •• General Chemistry: Chapter 10

26. - •• + + O≡N—O •• •• •• 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. General Chemistry: Chapter 10

30. + -½ -½ •• •• •• O O O •• •• 10-5 Resonance - - + + •• •• •• •• •• •• O O O O O O •• •• •• •• •• •• Electrostatic potential map of ozone General Chemistry: Chapter 10

32. 10-6 Exceptions to the Octet Rule • Odd-ElectronSpecies •• •• • N=O •• H •• O—H • H—C—H •• • General Chemistry: Chapter 10

33. •• •• •• F •• •• F •• + - B B •• - •• •• •• •• F F •• •• F F + •• •• •• •• •• •• •• Incomplete Octets •• •• F •• B •• •• F F •• •• •• •• General Chemistry: Chapter 10

34. •• •• •• F •• Cl •• •• •• •• •• •• F •• •• Cl F •• Cl •• •• •• •• •• S P •• •• •• F F •• •• Cl Cl •• •• F •• •• •• •• •• •• •• •• Expanded octets •• •• Cl •• P •• •• •• Cl Cl •• •• •• •• General Chemistry: Chapter 10

35. Expanded Valence Shells General Chemistry: Chapter 10

36. 10-7 The Shapes of Molecules In H2O the bond lengths d1= d2 = 95.8 pm and the bond angle is α= 104.45°. FIGURE 10-9 • Geometric shape of a molecule General Chemistry: Chapter 10

37. Bond length – distance between nuclei. • Bond angle – angle between adjacent bonds. • 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. General Chemistry: Chapter 10

38. FIGURE 10-10 Balloon analogy to valence-shell electron-pair repulsion General Chemistry: Chapter 10

39. Methane, Ammonia and Water General Chemistry: Chapter 10

40. FIGURE 10-12 Several electron-group geometries illustrated General Chemistry: Chapter 10

41. Table 10.1 Molecular Geometry as a Function of Electron Group Geometry General Chemistry: Chapter 10

42. General Chemistry: Chapter 10

43. General Chemistry: Chapter 10

44. General Chemistry: Chapter 10

45. General Chemistry: Chapter 10

46. Replace this part of table 10.1 this format is not present in the text. Parent table is on page 425 and 426 General Chemistry: Chapter 10

48. Applying VSEPR Theory • Draw a plausible Lewis structure. • Determine the number of e- groups and identify them as bond or lone pairs. • Establish the e- group geometry. • Determine the molecular geometry. General Chemistry: Chapter 10

49. •• •• •• + + S S S - •• •• •• - •• O O O •• •• •• •• O O O •• •• •• •• •• •• •• •• Structures with Multiple Covalent Bonds 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. General Chemistry: Chapter 10