Chemistry: Bonding

1. Chemistry: Bonding

2. Ionization Energy Energy required to remove 1 mole of electrons from 1 mole of atoms

3. Nonmetals Metals Ionization Energy Trend F Nonmetals: gain e- have high Ionization Energies Which element has the highest ionization energy? Metals: lose e- have the lowest Ionization Energies

4. Electronegativity Measure of attraction of an atom for electrons Atoms have equal electronegativity This one has a higher electronegativity This one has a MUCH higher electronegativity

5. F Nonmetals Metals Fr Electronegativity Trend Fluorine has the greatest Electronegativity (attraction for electrons) Francium has the lowest Electronegativity

6. Electronegativity Practice 1) Draw in the bonding electrons Example— H : F (bonding electrons closer to F) Try these: Zn Br Na Cl 2) Arrange from lowest to highest electronegativities: a) F(9), Sb(51), In(49), Se(34) smallest largest answer: b) Ga (31), Fr(87), P(15), Ge(32), Zn(30) smallest largest answer: : : In Sb Se F Fr Zn Ga Ge P

7. Which has a greater electronegativity: a metal or a non-metal? Which is more electronegative: Cu or S? Br or Ga?

8. Polarity d What is polarity? Separation of charge Symbol: d (Greek “delta”) Meaning: “partial” d + d- Example: Cu : O What causes polarity? An unequal attraction toward the electrons

9. Polar Molecules • Have distinguishable sides; or opposite ends • Can identify a top/bottom or right/left side • Asymmetrical

10. Nonpolar Molecules • Symmetrical • Equal distribution of charge • No d+ or d- • One side NOT distinguishable • Everything is the same around a central part

11. e - e - + + Chemical Bonding • Attraction between atoms • Electrostatic attraction (opposites attract) (+) to (-) • an atom’s protons are attracted to another atom’s electron

12. Pauling Electronegativity Values Bond Types • Determined by difference in electronegativity values—absolute value of DEN

13. Bond Types • Ionic • Covalent • Metallic

14. Cl Cl Na +1 -1 Na Ionic Bonds Electrons are TRANSFERRED from a metal to a non-metal electrostatic attraction

15. Pauling Electronegativity Values Ionic Bonds: DEN > 1.7 DEN = 4.0 – 1.0 = 3.0 DEN = 3.5-1.0 = 2.5 Example: Sr – F Example: Li—O Acids, Bases, and Salts are Ionic compounds

16. Characteristics of Ionic Substances • VEEEERRRRRYYYY strong bonds • High melting points • Water soluble • Conduct electricity as liquids and in solution • Form defined crystals

18. Covalent Bonds Formed by two or more atoms sharing an electron pair

19. e - e - + + Covalent Bonds Usually formed by two non-metals (similar electronegativities) Electrostatic attraction between atoms A MOLECULE is two or more atoms covalently bonded

20. Covalent Bonds: DEN < 1.7 Si—C DEN = 0.7 F—F DEN = 0.0

21. Characteristics of Covalent Substances Low melting points Do not conduct electricity Brittle

22. Types of Covalent Bonds 1. Non-polar Covalent 2. Polar Covalent

23. Types of Covalent Bonds 1. Non-polar Covalent equal sharing of e- pair all diatomic molecules: Cl2, H2, Br2, I2 Why? DEN = 0

24. Types of Covalent Bonds 2. Polar Covalent unequal sharing of e- pair DEN : 0.3-1.7

25. Practice Problems In H2S, which attracts electrons more?______ What is the approximate DEN? _____ S 0.3

26. Metallic Bonds Characterized by free moving electrons Found, obviously, in metals Very strong bond

27. Summary Identify the bond type in: CaF2 CuCl polar-covalent ionic

28. Lab 28 Part 1 Results P NP P NP NP P P NP & P NP NP

29. Lab 28 Part 2 Results P NP P NP BOTH P P NP BOTH NP

30. Lewis Dot Diagrams Which electrons do dot diagrams symbolize? outer electrons—valence electrons (s and p orbitals)

31. H H H H Arsenic Dot Diagram? How many bonds can Arsenic form? Dot Diagram for Hydrogen? How many bonds can Hydrogen form? 3 1

32. As H H H Note: each “ “ is an electron pair As H H H Arsenic Trihydride, AsH3 or

33. or O H or O H O O H H or H H Oxygen Dot Diagram? How many bonds can Oxygen form? Draw H2O 2

34. B Boron Dot Diagram? How many bonds can Boron form? Dot Diagram for Cl? How many bonds can Cl form? 3 1

35. Boron Trichloride, BCl3

36. Si I Silicon Dot Diagram? How many bonds can Silicon form? Dot Diagram for I? How many bonds can I form? 4 1

37. I I Si Si I I I I I I SiI4

38. Bond Angles & Bond Length Bond Length O H H Bond Angle

39. Molecular Shapes Pair Repulsion (VSEPR) Stands for: Valence Shell Electron Pair Repulsion e- pairs repel each other and spread out as much as possible

40. Linear 2 outer electron pairs Group IIA Bond Angle = 180o Ex: BeCl2

41. Linear—double bonds Ex. CO2 In both, the shape is determined by electron repulsion

42. Trigonal Planar 3 outer electron pairs Group III A Bond Angle = 120o Ex: BCl3

43. Trigonal Planar—double bonds H2CO

44. Tetrahedron 4 outer e- pairs Consider paired (bonding) e- pairs & unpaired e- pairs (“lonepairs”)

45. Perfect Tetrahedron ALL 4 e- pairs around central atom are bonded Ex: CH4 Bond Angle = 109.5o

46. .. Pyramidal 4 e- pairs—3 bonded and 1 lone pair Ex: NH3 Bond Angle = 107o

47. O H H 5 Bent 4 e- pairs —2 bonded and 2 lone pairs Ex: H2O Bond Angle = 104.5o

48. Write dot diagrams for the following molecules: Determine the molecular shape, bond angles, and polarity   PBr3 CH4   H2O BeI2 AlCl3 CO2 H2S SiF4

49. P Br Br Br PBr3 d+ • Pyramidal • 107o • polar d-

50. O H H H2O • Bent • 104.5o • Polar d- d+