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Chapter 16 Covalent Bonding

Chapter 16 Covalent Bonding. Milbank High School. Section 16.1 The Nature of Covalent Bonding. OBJECTIVES: Describe and give examples of coordinate covalent bonding, resonance structures, and exceptions to the octet rule. Section 16.1 The Nature of Covalent Bonding. OBJECTIVES:

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Chapter 16 Covalent Bonding

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  1. Chapter 16Covalent Bonding Milbank High School

  2. Section 16.1The Nature of Covalent Bonding • OBJECTIVES: • Describe and give examples of coordinate covalent bonding, resonance structures, and exceptions to the octet rule.

  3. Section 16.1The Nature of Covalent Bonding • OBJECTIVES: • Use electron dot structures to show the formation of single, double, and triple covalent bonds.

  4. + + How does H2 form? • The nuclei repel

  5. + + How does H2 form? • The nuclei repel • But they are attracted to electrons • They share the electrons

  6. Covalent bonds • Nonmetals hold on to their valence electrons. • Get noble gas configuration by sharing valence electrons with each other. • By sharing, both atoms get to count the electrons toward a noble gas configuration.

  7. F Covalent bonding • Fluorine has seven valence electrons

  8. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven

  9. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons…

  10. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons…

  11. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons…

  12. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons…

  13. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons…

  14. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons… • …both end with full orbitals

  15. Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons… • …both end with full orbitals F F 8 Valence electrons

  16. Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons… • …both end with full orbitals F F 8 Valence electrons

  17. A Single Covalent Bond is... • A sharing of two valence electrons. • Only nonmetals and Hydrogen. • Different from an ionic bond because they actually form molecules.

  18. H O Water Each hydrogen has 1 valence electron Each hydrogen wants 1 more The oxygen has 6 valence electrons The oxygen wants 2 more They share to make each other happy

  19. O Water • The oxygen still wants one more H

  20. O Water • The second hydrogen attaches • Every atom has full energy levels H H Sample 16-1, p.440

  21. Multiple Bonds • Double bonds - share two pairs (4 total) of electrons • Triple bond - share three pairs (6 total) of electrons • Table 16.1, p.443 - Know which elements are diatomic (Oxygen?)

  22. O Carbon dioxide • CO2 - Carbon is central atom( more metallic ) • Carbon has 4 valence electrons • Wants 4 more • Oxygen has 6 valence electrons • Wants 2 more C

  23. O Carbon dioxide • Attaching 1 oxygen leaves the oxygen 1 short, and the carbon 3 short C

  24. O O Carbon dioxide • Attaching the second oxygen leaves both oxygen 1 short and the carbon 2 short C

  25. O O Carbon dioxide • The only solution is to share more C

  26. O O Carbon dioxide • The only solution is to share more C

  27. O Carbon dioxide • The only solution is to share more O C

  28. O Carbon dioxide • The only solution is to share more O C

  29. O Carbon dioxide • The only solution is to share more O C

  30. Carbon dioxide • The only solution is to share more O C O

  31. Carbon dioxide • The only solution is to share more • Requires two double bonds • Each atom can count all the electrons in the bond O C O

  32. Carbon dioxide • The only solution is to share more • Requires two double bonds • Each atom can count all the electrons in the bond 8 valence electrons O C O

  33. Carbon dioxide • The only solution is to share more • Requires two double bonds • Each atom can count all the electrons in the bond 8 valence electrons O C O

  34. Carbon dioxide • The only solution is to share more • Requires two double bonds • Each atom can count all the electrons in the bond 8 valence electrons O C O

  35. Examples • Draw in the bonds • All 8 electrons are accounted for • Everything is full H H N H

  36. HCN • Put single bond between each atom • Need to add 2 more bonds • Must go between C and N H C N

  37. HCN • Put in single bonds • Need 2 more bonds • Must go between C and N • Uses 8 electrons - 2 more to add to equal the 10 it has H C N

  38. HCN • Put in single bonds • Need 2 more bonds • Must go between C and N • Uses 8 electrons - 2 more to add • Must go on N to fill octet H C N

  39. Another way of indicating bonds • Often use a line to indicate a bond • Called a structural formula • Each line is 2 valence electrons H O H H O H =

  40. Structural Examples • C has 8 e- because each line is 2 e- • same for N • same for C here • same for O H C N H C O H

  41. C O A Coordinate Covalent Bond... • When one atom donates both electrons in a covalent bond. • Carbon monoxide • CO

  42. Coordinate Covalent Bond • When one atom donates both electrons in a covalent bond. • Carbon monoxide • CO C O

  43. Coordinate Covalent Bond • When one atom donates both electrons in a covalent bond. • Carbon monoxide • CO C O Shown as: C O

  44. Bond Dissociation Energies... • The total energy required to break the bond between 2 covalently bonded atoms • High dissociation energy usually means unreactive • Table 16.3, p448 • Sample: Calculate the kJ to dissociate the bonds in 0.5 mol CO2

  45. Resonance is... • When more than one valid dot diagram is possible. • Consider the two ways to draw ozone (O3)

  46. Exceptions to Octet rule • When there is an odd number of valence electrons • NO2 has 17 valence electrons, because the N has 5, and each O contributes 6 • impossible to satisfy octet, yet the stable molecule does exist

  47. Section 16.2Bonding Theories • OBJECTIVES: • Describe the molecular orbital theory of covalent bonding, including orbital hybridization.

  48. Section 16.2Bonding Theories • OBJECTIVES: • Use VSEPR theory to predict the shapes of simple covalently bonded molecules.

  49. VSEPR: stands for... • Valence Shell Electron Pair Repulsion • Predicts three dimensional geometry of molecules. • The name tells you the theory: • Valence shell - outside electrons. • Electron Pair repulsion - electron pairs try to get as far away as possible. • Can determine the angles of bonds.

  50. VSEPR • Single bonds fill all atoms. • There are 4 pairs of electrons pushing away. • The furthest they can get away is 109.5º H H C H H

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