1. Covalent Bonding Unit 11

2. Covalent Bonds Involve sharing outer energy level electrons.

3. How Are They Different Than Ionic? Ionic bonds work by electromagnetic attraction. A positively charged ion is attracted to a negative ion. Covalent bonds work by sharing electrons. They do not have charges, but are hard to separate due to this sharing.

4. Cl Cl How will two chlorine atoms react?

5. Cl Cl Each chlorine atom wants to gain one electron to achieve an octet

6. Cl Cl

7. Cl Cl

8. Cl Cl

9. Cl Cl octet

10. Cl Cl octet circle the electrons for each atom that completes their octets

11. Cl Cl The octet is achieved by each atom sharing the electron pair in the middle circle the electrons for each atom that completes their octets

12. Cl Cl The octet is achieved by each atom sharing the electron pair in the middle circle the electrons for each atom that completes their octets

13. Cl Cl This is the bonding pair circle the electrons for each atom that completes their octets

14. Cl Cl Single bonds are abbreviated with a dash circle the electrons for each atom that completes their octets

15. Cl Cl This is the chlorine molecule, Cl2 circle the electrons for each atom that completes their octets

16. Covalent Bonds Each oxygen has 6 valence electrons and wants two more to have a full octet. 6 electrons 6 electrons

17. Covalent Bonds If one oxygen shares two electrons with the other, the other has a full octet. 8 electrons – happy! 4 electrons left

18. Covalent Bonds But, then the other oxygen is short, so it pulls them back. Now the other oxygen shares 2 electrons 4 electrons left 8 electrons – happy!

19. Covalent Bonds Thus, by each of them sharing two electrons back and forth, they both are at the full octet simultaneously. 8 electrons 8 electrons

20. O O

21. O O

22. O O

23. O O

24. O O Both electron pairs are shared.

25. O O Both electron pairs are shared.

26. So Who Covalently Bonds? Alkaline or Alkali Earth Metals do not form covalent bonds! Also Halogens are rarely covalently bonded. Mostly it is non-metals in groups 3,4,5, and 6

27. Electron Distribution . . . C . Valence Electrons: 4 Electrons occur in 4 fours separated as far apart as possible

28. Electron Distribution . . . . . N C . . Valence Electrons: 4 5 Electrons occur in 4 fours separated as far apart as possible

29. Electron Distribution . . . . . N C . . O . . Valence Electrons: 4 5 6 Electrons occur in 4 fours separated as far apart as possible

30. Electron Distribution . . . . . N C . . O . . Valence Electrons: 4 5 6 Electrons occur in 4 fours separated as far apart as possible Secret Question: Why do electrons first fill orbitals one at a time before pairing up?

31. Electron Distribution . . . . . N C . . O . . Valence Electrons: 4 5 6 Electrons occur in 4 fours separated as far apart as possible Secret Question: Why do electrons first fill orbitals one at a time before pairing up? It is because electrons repel each other and want to be as far apart as possible.

32. Exception to Octet Rule Boron only has 3 valence electrons, so it is impossible to get to eight via covalent bonding Without 4 valence electrons, the shape of the molecule flattens out. BH3 B . . .

33. Single Bond Ethane is C2H6

34. Double Bond Ethene is C2H4

35. Triple Bond Acetylene is C2H2

36. Quadruple Bond??? Can not occur, because the last bond can not bend all the way around. Too far to bend Too far to bend Especially since triple bonds are so rigid

37. Possible Covalent Bonds Only where single electrons are located, can covalent bonds be made. Carbon has 4 single electrons, thus it can make 4 bonds. Nitrogen has 3 single electrons, thus it can make 3 bonds. Oxygen has 2 single electrons, thus it can make 2 bonds.

38. Double Bonds Revisited Since Oxygen can make two bonds, and Carbon can make four, it makes for some interesting combinations.

39. Why Carbon is the Key to Life It is precisely because carbon can make 4 bonds, as well as, double and triple bonds, that makes it so critical to life. Carbon chains can form virtually every formation possible.

40. DNA and the building blocks for life Carbon, plus two other flexible elements, oxygen and nitrogen form the backbone of DNA DNA contains the genetic code for the building of life out of the largest of all molecules, proteins.

41. Proteins are the largest molecules known