1. Covalent bonding Covalent bond: A chemical bond formed when two atoms share electrons.

2. Covalent bonding Covalent bond: A chemical bond formed when two atoms share electrons. Co means “together, joint, jointly.”

3. Covalent bonding Covalent bond: A chemical bond formed when two atoms share electrons. Co means “together, joint, jointly.” Double bond: When two pairs of electrons are shared between atoms.

4. Covalent bonding Covalent bond: A chemical bond formed when two atoms share electrons. Co means “together, joint, jointly.” Double bond: When two pairs of electrons are shared between atoms. Molecular compounds: Molecules formed through covalent bonding.

5. Electron dot diagram COHNFCOHNF

6. COHNF Review: What number of valence electrons do atoms want in order to be stable?

7. Electron dot diagram COHNF Review: What number of valence electrons do atoms want in order to be stable? Answer: 0 or 8

8. Electron dot diagram COHNF Atoms want 0 or 8 valence electrons to be stable. However, there are two exceptions: hydrogen and helium. They are stable when their inner shell of 2 is filled.

9. Atoms want 0 or 8 valence electrons to be stable. However, there are two exceptions: hydrogen and helium. They are stable when their inner shell of 2 is filled. Helium

10. Thus hydrogen only needs one more valence electron to be stable. Helium is already stable.

11. F Examples of covalent bonds/molecular compounds

12. F F2F2

13. Examples of covalent bonds/molecular compounds F FO F2F2

14. Examples of covalent bonds/molecular compounds F FO H H F2F2

15. Examples of covalent bonds/molecular compounds F FO H H Water molecule H 2 0 F2F2

16. Examples of covalent bonds/molecular compounds O

17. O

18. Examples of covalent bonds/molecular compounds O Oxygen molecule O 2 (double bond)

19. Examples of covalent bonds/molecular compounds O Oxygen molecule H 2 0 (double bond) H3NH3N

20. Examples of covalent bonds/molecular compounds O Oxygen molecule H 2 0 (double bond) N H3NH3N

21. Examples of covalent bonds/molecular compounds O Oxygen molecule H 2 0 (double bond) NH H3NH3N H H

22. Examples of covalent bonds/molecular compounds C0 2

23. Examples of covalent bonds/molecular compounds C0 2 C

24. Examples of covalent bonds/molecular compounds O C0 2 C

25. Examples of covalent bonds/molecular compounds O C0 2 CO

26. Examples of covalent bonds/molecular compounds O C0 2 CO double bond

27. Examples of covalent bonds/molecular compounds N N2N2

28. N N2N2

29. N N2N2 N

30. N N2N2 triple bond (this is the maximum number of bonds possible) N

31. More about molecular compounds Atoms in molecular compounds do not have strong plus-minus charges. Thus less heat is needed to melt or boil molecular solids. Salt (an ionic compound) melts at 801° C. Sugar (a molecular compound) melts at 185° C.

32. Because electrons do not move between the atoms, molecular compounds do not conduct electricity well.

33. This includes compounds such as rubber and water, which do not conduct electricity.

34. Polar molecular compounds Some atoms pull more strongly on the shared electrons than other atoms do.

35. Polar molecular compounds Some atoms pull more strongly on the shared electrons than other atoms do. As a result, the valence electrons move closer to the stronger atoms.

36. Polar molecular compounds Some atoms pull more strongly on the shared electrons than other atoms do. As a result, the valence electrons move closer to the stronger atoms. Since electrons have a negative charge, the strong atom will now have a slightly negative charge, and the weaker atom a slightly positive charge.

37. Nonpolar bond F F Equal pull

38. Polar bond H F Unequal pull + -

39. Water is a polar bond Electrons are pulled toward the oxygen atom.

40. Water is a polar bond Electrons are pulled toward the oxygen atom. This causes cohesion: The attraction that occurs between particles of the same substance.

41. Can you think of examples of water’s cohesion (holding together)?

42. Water droplets

43. Can you think of examples of water’s cohesion (holding together)? Surface tension

44. Can you think of examples of water’s cohesion (holding together)? Water transport in plants http://www.youtube.com/watch?v=CT4pURpXkbY

45. Why don’t oil and water mix?

46. The polar water molecules are attracted more strongly to each other than they are to the nonpolar oil molecules.

47. Why don’t oil and water mix? The polar water molecules are attracted more strongly to each other than they are to the nonpolar oil molecules. Soap molecules are polar on one end and nonpolar on the other.

48. Why don’t oil and water mix? The polar water molecules are attracted more strongly to each other than they are to the nonpolar oil molecules. Soap molecules are polar on one end and nonpolar on the other.