1. Dipoles and Polar Molecules
Page 80
Link to Phet Polar Molecules

2. Dipole An uneven distribution of electron density a molecule.
Results in a partial + and partial - .
Direction of dipole shown by arrow pointing toward negative end (cross on arrow near + end)

3. Polar Molecules Step 1: Lewis Dot (water)
Molecules with a “net” or total dipole.
Three steps in determining polarity:
Step 1: Lewis Dot (water)

4. Step 2: Geometry 2 2 Bonding Regions? Nonbonding Pairs?
Geometry is Bent or Angular 2 2
Link to VSEPR

5. Step 3: Examine arrangement of charges
Check for Symmetry of Charges
Step 3: Examine arrangement of charges
1) Polar Bonds : EN difference between atoms

6. If NO POLAR BONDS MOLECULE IS ALWAYS NONPOLAR
O2 NONPOLAR
EN O = 3.5; ∆EN = = 0

7. 2) Nonbonding (lone) Pairs on Central Atom
Regions of - charge
ONLY IMPORTANT IF OUTSIDE ATOMS ARE H

8. 3) Symmetry of Polar Bonds within Molecule:
If symmetric = NONPOLAR
NO NET DIPOLE
Carbon Dioxide
POLAR BONDS CANCEL; EQUAL AND OPPOSITE

9. Roping Analogy Equal and Opposite Forces

10. Concept of equal and opposite forces

11. 3) Symmetry of Polar Bonds within Molecule: NOT symmetric = POLAR
(overall or Net dipole)

12. If molecular geometry is not correct – symmetry may be misjudged
CORRECT! WATER IS BENT AND POLAR!!
WRONG!
Water is NOT LINEAR
and NONPOLAR

13. Water

14. All identical outside atoms + NO nonbonding pairs on central atom= symmetric (non-polar)

15. Sample Polarities
Link to video polarities and shapes