Unit 2 Atoms and Bonding
2.91 Molecular Shapes and
VSEPRs
Textbook ch 9.1 – 9.2
Big Idea 2: Chemical and physical properties of materials can be
explained by the structure and the arrangement of atoms, ions, or
molecules and the forces between them. Students will be able to
demonstrate understanding by laboratory investigation, analysis of
data and creation of models.
Learning Objectives
SWBAT:
:
• Predict the 3D shapes of molecules using
VSPER model
Molecular
Geometry
Hemoglobin
SHAPES
• This is the 3-D shape of a molecule
• Electrons repel each other
– Because of this, they adjust their shape
to be as far apart as possible
• Electrons will repel away from each
other to lower the repulsion in the
molecule
VSEPR Model
(Valence Shell Electron Pair Repulsion)
The structure around a given atom
is determined principally by
minimizing electron pair repulsions.
Predicting a VSEPR Structure
 Draw Lewis structure.
 Put pairs as far apart as possible.
 Determine positions of atoms from the
way electron pairs are shared
 Determine the name of molecular
structure from positions of the atoms.
Take out worksheet
Skeleton
AX
Shape
Linear
Examples
# atoms bonded
to central
atom:
# Unbonded
pairs of
:
electrons
H2
Picture
Skeleton
AX2
Shape
Linear
Examples
# atoms bonded
to central
atom:
# Unbonded
pairs of
:
electrons
CO2
Picture
Skeleton
Shape
AX3 Trigonal
planar
Examples
# atoms bonded
to central
atom:
# Unbonded
pairs of
:
electrons
BF3
Picture
Skeleton
Shape
AX2E bent
Examples
# atoms bonded
to central
atom:
# Unbonded
pairs of
:
electrons
SO2
Picture
Skeleton
AX4
Shape
tetrahedral
Examples
# atoms bonded
to central
atom:
# Unbonded
pairs of
:
electrons
CH4
Picture
Skeleton
AX3E
Shape
Trigonal
pyramidal
Examples
# atoms bonded
to central
atom:
# Unbonded
pairs of
:
electrons
NH3
Picture
Skeleton
Shape
AX2E2 bent
Examples
# atoms bonded
to central
atom:
# Unbonded
pairs of
:
electrons
H2O
Picture
Skeleton
Shape
AXE3 linear
Examples
# atoms bonded
to central
atom:
# Unbonded
pairs of
:
electrons
HCl
Picture
Skeleton
AX5
Shape
Trigonal
bipyramidal
Examples
# atoms bonded
to central
atom:
# Unbonded
pairs of
:
electrons
PCl5
Picture
Skeleton
Shape
AX4E Seesaw
Examples
# atoms bonded
to central
atom:
# Unbonded
pairs of
:
electrons
SF4
Picture
Skeleton
Shape
AX3E2 T shape
Examples
# atoms bonded
to central
atom:
# Unbonded
pairs of
:
electrons
ClF3
Picture
Skeleton
Shape
AX2E3 linear
Examples
# atoms bonded
to central
atom:
# Unbonded
pairs of
:
electrons
XeF2
Picture
Skeleton
AX6
Shape
octahedral
Examples
# atoms bonded
to central
atom:
# Unbonded
pairs of
:
electrons
SF6
Picture
Skeleton
Shape
AX5E Square
pyramidal
shape
Examples
# atoms bonded
to central
atom:
# Unbonded
pairs of
:
electrons
BrF5
Picture
Skeleton
Shape
AX4E2
square
planar
Examples
# atoms bonded
to central
atom:
# Unbonded
pairs of
:
electrons
XeF4
Picture
References
http://www.sciencegeek.net/Chemistry/Powerpoints2.shtml
I modified his original PPT to fit our needs in AP
Chemistry needs.
Our textbook: Brown, Lemay et all. AP edition
chemistry, 13th edition, 2015