Download electron domain geometry

CHM 101 – Chapter Nine
1. Molecular shapes and the VSEPR model
Department of Chemistry and Biochemistry
CHM 101 - Reeves
VSEPR
Many geometric shapes recur in nature
Department of Chemistry and Biochemistry
CHM 101 - Reeves
VSEPR
Atoms in molecules are surrounded by electron domains
consisting of lone pairs and chemical bonds.
Cl
Cl
O
C
Cl
Cl
S
O
sulfur
trioxide
carbon
tetrachloride
Lone pairs
O
Bonding pairs
Department of Chemistry and Biochemistry
Multiple bond
CHM 101 - Reeves
VSEPR
•
Because these domains are negatively charged,
they repel one another.
•
Their repulsive energy is minimized by arranging
them as far from each other as possible.
•
According to VSEPR, molecular shapes result
from geometries that enable the maximum
distance between electron domains.
Electron domains consist of lone pains and
bonding pairs with multiple bonds counting as
one domain.
•
Department of Chemistry and Biochemistry
CHM 101 - Reeves
Molecular Shapes
2 electron domains
3 electron domains
6 electron domains
4 electron domains
Department of Chemistry and Biochemistry
5 electron domains
CHM 101 - Reeves
Molecular Shapes
H
H
C
H
H
4 pairs
Department of Chemistry and Biochemistry
CHM 101 - Reeves
Molecular Shapes
H
H
O
S
C
H
O
H
Department of Chemistry and Biochemistry
O
CHM 101 - Reeves
Molecular Shapes
H
H
O
O
S
C
H
H
O
Department of Chemistry and Biochemistry
Cl
Cl
P
Cl
Cl
Cl
CHM 101 - Reeves
Molecular Shapes
Although the number of electron domains
surrounding an atom determines it's bond angles
and overall shape, electrons cannot be "seen".
For this reason, two types of geometries must be
considered:
• The electron domain geometry is the shape
around the central atom determined by the total
number of electron domains.
• The molecular geometry is defined by the
number of atoms that surround the central atom.
Department of Chemistry and Biochemistry
CHM 101 - Reeves
Molecular Shapes
Although the number of electron domains
surrounding an atom determines it's bond angles
and overall shape, electrons cannot be "seen".
H
N H
H
Department of Chemistry and Biochemistry
CHM 101 - Reeves
Molecular Shapes
Although the number of electron domains
surrounding an atom determines it's bond angles
and overall shape, electrons cannot be "seen".
H
N H
H
Department of Chemistry and Biochemistry
H
O
H
CHM 101 - Reeves