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Dipoles and Polar Molecules

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Presentation on theme: "Dipoles and Polar Molecules"— Presentation transcript:

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


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