1. Example: water
(bent shape)

2. Example: water
(bent shape)

3. Example: water
net dipole
(bent shape)

4. Example: water
net dipole
(bent shape)
The dipole moment of water is 1.8 D, which is a relatively large value.

5. Example: water
net dipole
(bent shape)
The dipole moment of water is 1.8 D, which is a relatively large value. For this reason, water is an excellent solvent for ionic species.

6. If water were linear, that is

7. If water were linear, that is
The dipole moment would be ?

8. If water were linear, that is
The dipole moment would be ?
The molecule would polar or nonpolar?

9. If water were linear, that is
The dipole moment would be ?
The molecule would polar or nonpolar?
The consequence would be?

10. If water were linear, that is
The dipole moment would be ?
zero
The molecule would polar or nonpolar?
The consequence would be?

11. If water were linear, that is
The dipole moment would be ?
zero
The molecule would polar or nonpolar?
nonpolar
The consequence would be?

12. If water were linear, that is
The dipole moment would be ?
zero
The molecule would polar or nonpolar?
nonpolar
The consequence would be?
You would be dead!

13. Electronegativity

14. Electronegativity
Electronegativity: The ability of an atom in a molecule to attract electrons towards itself.

15. Electronegativity
Electronegativity: The ability of an atom in a molecule to attract electrons towards itself. The values of the electronegativity depend on the ionization energy, the electron affinity, and also the nature of the bonding orbitals.

16. The difference in electronegativity provides an estimate of the degree of polarity of a bond.

17. The difference in electronegativity provides an estimate of the degree of polarity of a bond. The relative values of the electronegativities indicate which end of the bond carries the negative charge.

18. The difference in electronegativity provides an estimate of the degree of polarity of a bond. The relative values of the electronegativities indicate which end of the bond carries the negative charge. Example: In H2O the oxygen atom is more electronegative than hydrogen(3.5 on the Pauling scale for O, and 2.1 for H), therefore the bond dipoles are:

22. Ionic Bonds

23. Ionic Bonds
Ionic Bond: Results from the electrostatic attraction between a cation and an anion in an ionic compound.

24. Ionic Bonds
Ionic Bond: Results from the electrostatic attraction between a cation and an anion in an ionic compound.
Consider compounds in which the two atoms differ significantly in electronegativity, e.g. LiF.

25. The electronic configuration of Li is 1s22s1 and that of F is 1s22s22p5.

26. The electronic configuration of Li is 1s22s1 and that of F is 1s22s22p5. When Li and F atoms come into contact with each other, a reaction takes place in which the outer 2s1 valence electron on Li is transferred to the F atom to form LiF.

27. The electronic configuration of Li is 1s22s1 and that of F is 1s22s22p5. When Li and F atoms come into contact with each other, a reaction takes place in which the outer 2s1 valence electron on Li is transferred to the F atom to form LiF.
Li+ + F-
1s22s s22p s s22p6
(Core electrons on F not shown.)

28. The electronic configuration of Li is 1s22s1 and that of F is 1s22s22p5. When Li and F atoms come into contact with each other, a reaction takes place in which the outer 2s1 valence electron on Li is transferred to the F atom to form LiF.
Li+ + F-
1s22s s22p s s22p6
(Core electrons on F not shown.)

30. For the reaction of lithium with difluorine, the reaction can be written as:
Li+F-

31. For the reaction of lithium with difluorine, the reaction can be written as:
Li+F-

32. For the reaction of lithium with difluorine, the reaction can be written as:
Li+F-
LiF is held together by the attractive electrostatic forces between the cation Li+ and the anion F-.

33. There is no sharp separation between ionic bond and covalent bond
There is no sharp separation between ionic bond and covalent bond. It is common to talk about the percentage ionic character.

36. There is no sharp separation between ionic bond and covalent bond
There is no sharp separation between ionic bond and covalent bond. It is common to talk about the percentage ionic character.
The percent ionic character of a bond can be approximately estimated as follows:

37. There is no sharp separation between ionic bond and covalent bond
There is no sharp separation between ionic bond and covalent bond. It is common to talk about the percentage ionic character.
The percent ionic character of a bond can be approximately estimated as follows:
For HF the dipole moment is 1.91 D and the bond length is Å. What is the % ionic character?
Use the equation

40. = 6.95 x 10-20C

41. = 6.95 x 10-20C
Now for complete transfer of one electron from the H atom to the F atom, the charge Q would be the magnitude of the electronic charge, that is Q = x 10-19C.

42. The per cent ionic character can be approximated as

43. The Covalent Bond

44. The chemistry of carbon
The Covalent Bond
The chemistry of carbon

45. Modern Theories of Bonding
The Covalent Bond
The chemistry of carbon
Modern Theories of Bonding

46. Lewis structures tell us nothing about why covalent bonds are formed, why the octet rule is usually satisfied, and why it can sometimes be violated.

47. Lewis structures tell us nothing about why covalent bonds are formed, why the octet rule is usually satisfied, and why it can sometimes be violated. Modern theories describe the bonds between atoms in terms of what happens to atomic orbitals when the atoms are joined together.

48. There are two basic theories:
1. Valence Bond Theory

49. There are two basic theories:
1. Valence Bond Theory
2. Molecular Orbital Theory

50. Valence bond theory imagines individual atoms, each with their orbitals and electrons, coming together and forming covalent bonds.

51. Valence bond theory imagines individual atoms, each with their orbitals and electrons, coming together and forming covalent bonds.
Molecular orbital theory, by comparison, does not examine how the molecule is formed. It views a molecule as a collection of positive nuclei surrounded in some way by a set of molecular orbitals.

52. Atomic orbitals are centered on a particular atom
Atomic orbitals are centered on a particular atom. Molecular Orbital: An orbital that is spread out over the entire molecule, or a significant fraction of a molecule.

53. Valence Bond Theory
According to valence bond theory, a bond between two atoms is formed by the overlap of two atomic orbitals, one provided by each atom.

54. Valence Bond Theory
According to valence bond theory, a bond between two atoms is formed by the overlap of two atomic orbitals, one provided by each atom.
Overlap means that portion of the two orbitals that share the same space.

55. A maximum of two electrons with their spins paired, can be shared between the overlapped orbitals.

56. A maximum of two electrons with their spins paired, can be shared between the overlapped orbitals.
The strength of the bond, and the extent to which the energy of the isolated atoms is lowered is determined in part by the extent to which the orbitals overlap.

57. Atoms tend to position themselves so that the maximum amount of overlap occurs.*
The picture of bond formation for H2. +

58. Atoms tend to position themselves so that the maximum amount of overlap occurs.*
The picture of bond formation for H2. +
1s s
separated H atoms H2

59. Atoms tend to position themselves so that the maximum amount of overlap occurs.*
The picture of bond formation for H2. +
1s s
separated H atoms H2
* Subject to the constraints of the other electrostatic interactions that are present.