1. Polar Molecules
Section 4.4

2. Polar Bonds
Polar Bonds - look up electronegativity values for each element on the periodic table, then determine the difference:
<0.4 non-polar bond
polar bond
1.8+ Ionic bond (only if a non-metal and a metal)

3. Examples
Are the following bonds polar?
HBr BH3

4. Polar Molecules
Polar Molecules – have polar bonds and the molecule is not symmetrical (i.e. the charges are not shared equally around the central atom) Use VSPER
Non-polar molecules – can have polar or non-polar bonds that are equally shared around the central atom.

5. Empirical Rules for Polar & Non-polar Molecules
Formula
Description
Example
Polar AB
Linear Molecules
CO, HCl
CxAyBz
Molecules containing C and 2 other types of atoms
C2H5OH
CHCl3
OxAy
Molecules with an O at one end
H2O
NxAy
Molecules with an N at one end
NH3
Non-polar A2
Diatomic molecules of the same element O2
CxAy
Most carbon compounds
CO2

6. Examples
NCl3
Polar
CO2
Non-polar
H2O

7. Applying VSEPR
Both shape and bond polarity will determine if the molecule is polar.
If the molecule is symmetrical the molecule will be non-polar.
A bond dipole is the new way to show the polar bond (they are vectors…)

8. A quick review of Vectors=

9. Theoretical Prediction of Molecular Polarity
Draw a Lewis Structure
Use VSEPR to determine the shape around each central atom
Use electronegativities to determine the polarity of each bond.
Add the bond dipole vectors and determine if the resultant is 0 (non-polar) or not 0 (polar)

10. Examples
Are they polar or non-polar molecules?
SiBr4
SF2
BBr3

11. Today’s Tasks
Pg. 253 #1-3
Pg #6-10
Pg. 256 #1-3