Bellwork #4
10-15-2015
1. What is electronegativity?
2. The range of electronegativities for bonds is:
a) Ionic _____ to ______
b) Polar Covalent ______ to ______
c) Nonpolar Covalent ______ to ______
3. A molecule that is not symmetrical would be
classified as what kind of molecule?
4. Name and draw the lewis structure for SO2 and
describe the polarity of the bonds and the
molecule.
Bellwork #4
10-15-2015
Please put your take-home quiz on the front
bench!
Pick up a Shape Name Inquiry from the bench!
1. What does VSEPR stand for?
2. What is VSPER Theory?
3. How do you think electrons are responsible for
the shape of a molecule?
Chemical Bonding:
Molecular Geometry
How is molecular
geometry determined?
With VSEPR Theory!
VSEPR Theory is the idea that electron
groups repel one another.
V = Valence
S = Shell
E = Electron
P = Pair
R = Repulsion
What is an electron group?
An electron group can be defined as a
lone pair, single bond, double bond, or
triple bond.
Valence shell electron pair repulsion (VSEPR) model:
Predict the geometry of the molecule from the electrostatic
repulsions between the electron (bonding and nonbonding) pairs.
# of Electron # of Bonding
# lone
Groups on Groups around
pairs on
central atom central atom
central atom
2
2
Arrangement of
electron pairs
0
Molecular
Geometry
linear
linear
B
B
B
B
Example of LINEAR Molecular Geometry
0 lone pairs on central atom
Cl
Be
Cl
2 electron groups on central atom
VSEPR
# of Bonding
# lone
# of Electron Groups around
pairs on
central atom
Groups
central atom
3
3
0
3
2
1
Lone pair of electrons repels
the electrons in the bond and
pushes them down.
Arrangement of
electron pairs
trigonal
planar
Molecular
Geometry
trigonal
planar
Trigonal
planar
Bent
S
O
O
Example of TRIGONAL PLANAR
Molecular Geometry
VSEPR
# of Bonding
# lone
# of Electron Groups around
pairs on
central atom
Groups
central atom
4
4
4
4
3
2
0
Arrangement of
electron pairs
tetrahedral
tetrahedral
tetrahedral
trigonal
pyramidal
tetrahedral
bent
1
2
Molecular
Geometry
lone-pair vs. bonding
lone-pair vs. lone pair
bonding-pair vs. bonding
<
<
pair repulsion
repulsion
pair repulsion
Predicting Molecular Geometry
1. Draw Lewis structure for molecule.
2. Count number of electron groups on the central
atom. Compare the bonding groups to the lone pairs.
3. Use VSEPR to predict the geometry of the molecule.
What are the molecular geometries of SO2 and SO3?
O
S
Bent
O
O
O
S
O
Trigonal Planar