MOLECULAR GEOMETRY &
POLARITY
Chemistry 1/8/13
Drill

Draw a Lewis structure, a ball and stick model,
classify by shape, and give bond angle for:
 H2O
 BF3
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HW: Study for 25 pt “Quest”
Objectives
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IWBAT
 Define
VSEPR theory.
 Identify and construct molecular shapes – linear,
trigonal planar, tetrahedral, bent (trigonal planar),
trigonal pyramidal (tetrahedral), bent (tetrahedral)
 Classify molecules as polar or nonpolar by shape
Agenda
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Drill
Finish Lab – 10-15 minutes
Polarity Notes
Polarity Practice
Answer Qs for Quest
Closure
Using the Model Kits
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
Molecular Shapes Lab
The colors of the atoms are listed on the inside
cover of the model kit box.
 Use


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Nitrogen for Boron
Don’t put the model pieces in your mouth to remove
anything that is stuck.
I have pliers to remove “stuck” pieces.
If pieces fall on the floor, please stop and go after
them.
You have 10 minutes to finish the lab.
Polarity
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We know already that a bond may be polar (such
as polar covalent)
A molecule can also be polar!
What are the characteristics of polar molecules?
 Dissolve
in water (nonpolar molecules do NOT)
 Higher melting and boiling points (as compared to
nonpolar)
 Unequal sharing of electrons (as opposed to nonpolar)
How can we ID Polar molecules?
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Polar molecules tend to:
 Have
lone pairs on the central atom
AND/OR
 Be asymmetrical
AND/OR
 There are a large number of lone pairs on one side of
the molecule, but not the other.
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Example – CO2 vs. H2O, CH4 vs. CH3Cl
Let’s classify!
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Go through the lab and classify the compounds as
polar or nonpolar, based on their shapes.
HW Review

Review
 pg.
12
 pg. 10
Closure
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Give an example of:
A
polar, linear molecule
 A nonpolar, linear molecule
 A polar, tetrahedral molecule
 A nonpolar, tetrahedral molecule