Name: _____________________________________ Date: _______________________ Hour: ________________
Unit 7: Solutions and Water Chemistry
VSEPR and Molecular Shapes
VSEPR Theory tells us that the areas of a molecule that have a ____________
V=
S=
E=
P=
R=
concentration of _______________ will REPEL each other, and that these
repulsions will affect the _______________ of the molecule.
Tutorial Sketches
2 Atoms
3 Atoms
4 Atoms
What happened when the
3rd atom was moved?
5 Atoms
How many degrees apart
are the three attached
atoms?
3D Sketch:
Examples:
Carbon Dioxide, CO2
Nitrate Ion, NO3-
Sulfur Dioxide, SO2
Lewis Dot Diagram:
Lewis Dot Diagram:
Lewis Dot Diagram:
# of Areas of Electron Concentration?
# of Areas of Electron Concentration?
# of Areas of Electron Concentration?
Shape Name/Sketch:
Shape Name/Sketch:
Shape Name/Sketch:
Methane, CH4
Ammonia, NH3
Water, H2O
Lewis Dot Diagram:
Lewis Dot Diagram:
Lewis Dot Diagram:
# of Areas of Electron Concentration?
# of Areas of Electron Concentration?
# of Areas of Electron Concentration?
Shape Name/Sketch:
Shape Name/Sketch:
Shape Name/Sketch:
Reminder—Drawing Lewis Dot Diagrams
in 3 Easy Steps!
1. Count the # of valence electrons—add
them up for all atoms involved.
Drawing in 3D
How is the tetrahedral shape of methane drawn in 3D?
2. Make your skeleton—the “lonely” atom
is typically the center. Draw single bonds
to the other atoms.
Describe what you would use these to represent.
Solid lines:
3. Fill the octets of all atoms with the
remaining electrons! Exception: Hydrogen,
who only gets 2.
Wedges:
Dashes:
If you use up your valence electrons and
someone is still short, that is when you look
to add double bonds!
Homework:
1. What is the main idea behind VSEPR theory?
2. For each of the following, draw the Lewis Structure, identify the number of areas of electron concentration
(known as electron domains), give the shape name and a corrected 3D sketch.
CCl4
Lewis:
BH3
# Domains:
Shape & Sketch:
SiS2
Lewis:
# Domains:
Shape & Sketch:
Lewis:
# Domains:
Shape & Sketch:
PH3
Lewis:
# Domains:
Shape & Sketch:
Homework:
1. What is the main idea behind VSEPR theory?
Electron pairs in bonds or lone pairs repel each other, leading to different molecular
shapes!
2. For each of the following, draw the Lewis Structure, identify the number of areas of
electron concentration (known as electron domains), give the shape name and a
corrected 3D sketch.
CCl4 Lewis:
BH3 Lewis:
# Domains: 4
Shape & Sketch:
SiS2
# Domains: 3
Shape & Sketch: trigonal planar
tetrahedral
Lewis:
# Domains: 2
Shape & Sketch: linear
PH3
Lewis:
# Domains: 4
Shape & Sketch: trigonal pyramid