1. 1 Applied Physics And Chemistry Covalent bonding

2. 2 How does H 2 form? l The nuclei repel ++

3. 3 How does H 2 form? ++ l The nuclei repel l But they are attracted to electrons l They share the electrons

4. 4 Covalent bonds l Nonmetals hold onto their valence electrons. l They cant give away electrons to bond. l Still want noble gas configuration. l Get it by sharing valence electrons with each other. l By sharing both atoms get to count the electrons toward noble gas configuration.

5. 5 Covalent bonding l Fluorine has seven valence electrons F

6. 6 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven FF

7. 7 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons FF

8. 8 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons FF

9. 9 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons FF

10. 10 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons FF

11. 11 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons FF

12. 12 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons l Both end with full orbitals FF

13. 13 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons l Both end with full orbitals FF 8 Valence electrons

14. 14 Covalent bonding l Fluorine has seven valence electrons l A second atom also has seven l By sharing electrons l Both end with full orbitals FF 8 Valence electrons

15. 15 Single Covalent Bond l A sharing of two valence electrons. l Only nonmetals and Hydrogen. l Different from an ionic bond because they actually form molecules. l Two specific atoms are joined. l In an ionic solid you cant tell which atom the electrons moved from or to.

16. 16 How to show how they formed l Its like a jigsaw puzzle. l You put the pieces together to end up with the right formula. l For example- show how water is formed with covalent bonds.

17. 17 Water H O 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

18. 18 Water l Put the pieces together l The first hydrogen is happy l The oxygen still wants one more H O

19. 19 Water l The second hydrogen attaches l Every atom has full energy levels H O H

20. 20 Multiple Bonds l Sometimes atoms share more than one pair of valence electrons. l A double bond is when atoms share two pair (4) of electrons. l A triple bond is when atoms share three pair (6) of electrons.

21. 21 Carbon dioxide l CO 2 - Carbon is central atom l Carbon has 4 valence electrons l Wants 4 more l Oxygen has 6 valence electrons l Wants 2 more O C

22. 22 Carbon dioxide l Attaching 1 oxygen leaves the oxygen 1 short and the carbon 3 short O C

23. 23 Carbon dioxide l Attaching the second oxygen leaves both oxygen 1 short and the carbon 2 short O C O

24. 24 Carbon dioxide l The only solution is to share more O C O

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

26. 26 Carbon dioxide l The only solution is to share more O CO

27. 27 Carbon dioxide l The only solution is to share more O CO

28. 28 Carbon dioxide l The only solution is to share more O CO

29. 29 Carbon dioxide l The only solution is to share more O CO

30. 30 Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO

31. 31 Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO 8 valence electrons

32. 32 Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO 8 valence electrons

33. 33 Carbon dioxide l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond O CO 8 valence electrons

34. 34 Examples l NH 3 l N - has 5 valence electrons wants 8 l H - has 1 valence electrons wants 2 l NH 3 has 5+3(1) = 8 l NH 3 wants 8+3(2) = 14 l (14-8)/2= 3 bonds l 4 atoms with 3 bonds N H

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

36. 36 Examples l HCN C is central atom l N - has 5 valence electrons wants 8 l C - has 4 valence electrons wants 8 l H - has 1 valence electrons wants 2 l HCN has 5+4+1 = 10 l HCN wants 8+8+2 = 18 l (18-10)/2= 4 bonds l 3 atoms with 4 bonds -will require multiple bonds - not to H

37. 37 HCN l Put in single bonds l Need 2 more bonds l Must go between C and N NHC

38. 38 HCN l Put in single bonds l Need 2 more bonds l Must go between C and N l Uses 8 electrons - 2 more to add NHC

39. 39 HCN l Put in single bonds l Need 2 more bonds l Must go between C and N l Uses 8 electrons - 2 more to add l Must go on N to fill octet NHC

40. 40 Another way of indicating bonds l Often use a line to indicate a bond l Called a structural formula l Each line is 2 valence electrons HHO = HHO

41. 41 Structural Examples H CN C O H H l C has 8 electrons because each line is 2 electrons l Ditto for N l Ditto for C here l Ditto for O

42. 42 Coordinate Covalent Bond l When one atom donates both electrons in a covalent bond. l Carbon monoxide l CO OC

43. 43 Coordinate Covalent Bond l When one atom donates both electrons in a covalent bond. l Carbon monoxide l CO OC

44. 44 Coordinate Covalent Bond l When one atom donates both electrons in a covalent bond. l Carbon monoxide l CO OC

45. 45 How do we know if l Have to draw the diagram and see what happens. l Often happens with polyatomic ions and acids.

46. 46 Polar Molecules Molecules with ends

47. 47 Polar Molecules l Molecules with a positive and a negative end l Requires two things to be true ¬ The molecule must contain polar bonds This can be determined from differences in electronegativity. ­ Symmetry can not cancel out the effects of the polar bonds. Must determine geometry

48. 48 Is it polar? l HF lH2OlH2O l NH 3 l CCl 4 l CO 2

49. 49 Bond Dissociation Energy l The energy required to break a bond l C - H + 393 kJ C + H l We get the Bond dissociation energy back when the atoms are put back together If we add up the BDE of the reactants and subtract the BDE of the products we can determine the energy of the reaction ( H)

50. 50 Find the energy change for the reaction l CH 4 + 2O 2 CO 2 + 2H 2 O l For the reactants we need to break 4 C-H bonds at 393 kJ/mol and 2 O=O bonds at 495 kJ/mol= 2562 kJ/mol l For the products we form 2 C=O at 736 kJ/mol and 4 O-H bonds at 464 kJ/mol l = 3328 kJ/mol l reactants - products = 2562-3328 = -766kJ

51. 51 Intermolecular Forces What holds molecules to each other

52. 52 Intermolecular Forces l They are what make solid and liquid molecular compounds possible. l The weakest are called van der Waals forces - there are two kinds l Dispersion forces l Dipole Interactions –depend on the number of electrons –more electrons stronger forces –Bigger molecules

53. 53 Dipole interactions l Depend on the number of electrons l More electrons stronger forces l Bigger molecules more electrons Fluorine is a gas Bromine is a liquid Iodine is a solid

54. 54 Dipole interactions l Occur when polar molecules are attracted to each other. l Slightly stronger than dispersion forces. l Opposites attract but not completely hooked like in ionic solids.

55. 55 Dipole interactions l Occur when polar molecules are attracted to each other. l Slightly stronger than dispersion forces. l Opposites attract but not completely hooked like in ionic solids. HFHF HFHF

56. 56 Dipole Interactions

57. 57 Hydrogen bonding l Are the attractive force caused by hydrogen bonded to F, O, or N. l F, O, and N are very electronegative so it is a very strong dipole. l The hydrogen partially share with the lone pair in the molecule next to it. l The strongest of the intermolecular forces.

58. 58 Hydrogen Bonding H H O + - + H H O + - +

59. 59 Hydrogen bonding H H O H H O H H O H H O H H O H H O H H O