1. Electronegativity: Electron Distribution in a Bond
 Bonding Electrons NOT shared evenly.
Methanol C H O
More E.N.
Less E.N.
Electron density shifts in the direction of the more electronegative atom (oxygen).
Increased electron density

2. Electronegativity: Electron Distribution in a Bond
Figure 9.19 in text.
Methanol C H O
E.N. = 3.5
E.N. = 2.1
E.N. = 3.5 > E.N. = 2.1
More E.N.
Less E.N.
The O-H bond is a polar bond because it has + and – ends! + -
Dipole Moment Vector:
...an arrow that indicates the direction electrons shift.
...includes an additional mark to indicate positive end.
...usually drawn through the bond.

3. Polar Bonds: ComparisonsH
E.N. = 3.5
E.N. = 2.1
E.N. = 3.5 – 2.1 B H Na Cl
E.N. = 1.4
Polar Covalent
E.N. = 2.0
E.N. = 2.1
E.N. = 0.9
E.N. = 3.0
E.N. = 2.1 – 2.0
E.N. = 3.0 – 0.9
E.N. = 0.1
E.N. = 2.1
Covalent
Ionic
Covalent <0.4
Polar Covalent 0.4 – 1.7
Pure Covalent
Ionic >1.7
E.N.
0.4
1.7