1. Chemical Bonding
Three main types:

2. Chemical Bonding
Three main types:
1. Covalent Bonding

3. Chemical Bonding 1. Covalent Bonding 2. Ionic Bonding
Three main types:
1. Covalent Bonding
2. Ionic Bonding

4. Chemical Bonding 1. Covalent Bonding 2. Ionic Bonding
Three main types:
1. Covalent Bonding
2. Ionic Bonding
3. Metallic Bonding

5. Chemical Bonding 1. Covalent Bonding 2. Ionic Bonding
Three main types:
1. Covalent Bonding
2. Ionic Bonding
3. Metallic Bonding
The focus will be on the first two.

6. Covalent Bonding

7. Covalent Bonding
An early view of the covalent bond.

8. Covalent Bonding
An early view of the covalent bond. Covalent bond: A bond in which two electrons are shared by two atoms.

9. Covalent Bonding
An early view of the covalent bond. Covalent bond: A bond in which two electrons are shared by two atoms. The key breakthroughs were made by Gilbert Lewis.

10. Lewis Structures

11. Lewis Structures
Lewis structure: A diagram showing how electron pairs are shared between atoms in a molecule.

12. Lewis Structures
Lewis structure: A diagram showing how electron pairs are shared between atoms in a molecule.
Consider the dihydrogen molecule.
H H

13. Lewis Structures
Lewis structure: A diagram showing how electron pairs are shared between atoms in a molecule.
Consider the dihydrogen molecule.
H H
The electron pair will be replaced with a line to designate the bond, so will be replaced by
H H

14. Lewis Structures
Lewis structure: A diagram showing how electron pairs are shared between atoms in a molecule.
Consider the dihydrogen molecule.
H H
The electron pair will be replaced with a line to designate the bond, so will be replaced by
H H
This is the Lewis structure for the dihydrogen molecule.

15. Covalent bond formation for H2

16. Distribution of electron density in H2

17. Only the valence electrons are represented in Lewis structures.

18. Only the valence electrons are represented in Lewis structures
Only the valence electrons are represented in Lewis structures. The difluorine molecule would be represented as

19. Only the valence electrons are represented in Lewis structures
Only the valence electrons are represented in Lewis structures. The difluorine molecule would be represented as and with the covalent bond shown, as

20. The Lewis structure for the water molecule is H H H H

21. The Lewis structure for the water molecule is H H H H The electrons that are not involved in bond formation are called nonbonding electrons or lone pairs.

22. The Lewis structure for the water molecule is H H H H The electrons that are not involved in bond formation are called nonbonding electrons or lone pairs. In F2 each F atom has three lone pairs and the O atom in water has two lone pairs.

23. There are many compounds in which the same two atoms share two or even three pairs of bonding electrons.

24. There are many compounds in which the same two atoms share two or even three pairs of bonding electrons. In these cases we have multiple bonding.

25. There are many compounds in which the same two atoms share two or even three pairs of bonding electrons. In these cases we have multiple bonding. The bond between two atoms sharing two pairs of electrons is called a double bond.

26. There are many compounds in which the same two atoms share two or even three pairs of bonding electrons. In these cases we have multiple bonding. The bond between two atoms sharing two pairs of electrons is called a double bond. Examples are O2 and CO2.

27. There are many compounds in which the same two atoms share two or even three pairs of bonding electrons. In these cases we have multiple bonding. The bond between two atoms sharing two pairs of electrons is called a double bond. Examples are O2 and CO2.

28. There are many compounds in which the same two atoms share two or even three pairs of bonding electrons. In these cases we have multiple bonding. The bond between two atoms sharing two pairs of electrons is called a double bond. Examples are O2 and CO2. C

29. Note that only the 2s and 2p electrons (valence electrons) are used in forming these bonds in O2 and CO2.

30. Note that only the 2s and 2p electrons (valence electrons) are used in forming these bonds in O2 and CO2. A triple bond arises when two atoms share three pairs of electrons.

31. Note that only the 2s and 2p electrons (valence electrons) are used in forming these bonds in O2 and CO2. A triple bond arises when two atoms share three pairs of electrons. Examples are N2 and C2H2.

32. Note that only the 2s and 2p electrons (valence electrons) are used in forming these bonds in O2 and CO2. A triple bond arises when two atoms share three pairs of electrons. Examples are N2 and C2H2.

33. Note that only the 2s and 2p electrons (valence electrons) are used in forming these bonds in O2 and CO2. A triple bond arises when two atoms share three pairs of electrons. Examples are N2 and C2H2. H C C H

34. The Octet Rule

35. The Octet Rule
If the number of electrons around each atom (except H) is counted for the previous examples, O2, F2, H2O, N2, CO2, C2H2, and a very large number of other examples, the number is 8.

45. This is equal to the number of electrons in the outer shell of the noble gases: ns2np6 (n 2).

46. This is equal to the number of electrons in the outer shell of the noble gases: ns2np6 (n 2). A complete shell of 2 (think about H) or 8 electrons represents a very stable electronic configuration. Based on this reasoning, Lewis formulated the octet rule.

47. This is equal to the number of electrons in the outer shell of the noble gases: ns2np6 (n 2). A complete shell of 2 (think about H) or 8 electrons represents a very stable electronic configuration. Based on this reasoning, Lewis formulated the octet rule. Octet rule: An atom other than H tends to form bonds until it is surrounded by eight valence electrons.

48. The octet rule is very useful for predicting the stabilities of molecules containing second-period elements, but it breaks down in a number of cases when applied to elements in the third period and beyond.

49. Rules for writing Lewis structures for molecules

50. 1. Write down the formula of the compound and determine which atom is bonded to which. Generally the structure must be chosen on the basis of experimental evidence.

51. 2. Draw the Lewis structures of the atoms:
Atom Number of Lewis structure
valence electrons Li

52. 2. Draw the Lewis structures of the atoms:
Atom Number of Lewis structure
valence electrons Li Be

53. 2. Draw the Lewis structures of the atoms:
Atom Number of Lewis structure
valence electrons Li Be B

54. 2. Draw the Lewis structures of the atoms:
Atom Number of Lewis structure
valence electrons Li Be B C

55. 2. Draw the Lewis structures of the atoms:
Atom Number of Lewis structure
valence electrons Li Be B C N

56. 2. Draw the Lewis structures of the atoms:
Atom Number of Lewis structure
valence electrons Li Be B C N O

57. 2. Draw the Lewis structures of the atoms:
Atom Number of Lewis structure
valence electrons Li Be B C N O F

58. 2. Draw the Lewis structures of the atoms:
Atom Number of Lewis structure
valence electrons Li Be B C N O F Ne

59. 3. Count the total number of valence electrons in the atoms involved.

60. 3. Count the total number of valence electrons in the atoms involved.
The total number of valence electrons is equal to the sum of the valence electrons of all the atoms.