Areas where electron pairs are most likely to be found.

1
VSEPR Models
Atoms in a molecules will try to orient
themselves as far apart as possible. Due to
electron density in the bond repelling other
electron dense areas. VSEPR Valence Shell
Electron Pair Repulsion. Paired valence
electrons push away from each other. Causes the
3D structure of the molecule.
Based on the total number of ELECTRON DOMAINS
around the central atom
Areas where
electron pairs are most likely to be
found. Either a single bond, multiple bond, or a
nonbonding pair of electrons
Electron domain
2
Domains shape Bonding pairs Non-bonding pairs- Molec geometry Bond angle



Linear
2
2
0
linear
180o
3
0
Trigonal planar
120o
Trigonal planar
3
Bent
2
1
120o
3
Domains shape Bonding pairs Non-bonding pairs Molec geometry Bond angle



4
Tetrahedral
4
0
Tetrahedral
109.5o
Trigonal pyramidal
3
1
109.5o
bent
109.5o
2
2
4
Domains shape Bonding pairs Non-bonding pairs Molec geometry Bond angle


Trigonal bipyramidal
5
Trigonal bipyramidal
5
0
120o 90o
Seesaw
1
4
120o 90o
Notice The three lobes are the ones that become
nonbonding pairs
Equatorial pairs
5
Domains shape Bonding pairs Non-bonding pairs Molec geometry Bond angle


T-shaped
5
Trigonal bipyramidal
3
2
120o 90o
Linear
3
2
180o
6
Domains shape Bonding pairs Non-bonding pairs Molec geometry Bond angle


Octahedral
6
Octahedral
6
0
90o
Square pyramidal
1
5
90o
Notice In this case, the Polars (top and
bottom) become nonbonding pairs first
7
Domains shape Bonding pairs Non-bonding pairs Molec geometry Bond angle


Square planar
6
Ocathedral
4
2
90o
T-shaped
3
3
120o 90o
Only time we deal with 5 and 6 domains are for
central atoms that can obtain more than an octet.
Only time we deal with 5 and 6 domains are for
central atoms that can obtain more than an octet.
8
Example Determine the molecular shape of the
following
CH4
H H C H H
Central atom has 4 domains, all as single bonds
tetrahedral
.. H N H H
4 domains, but only 3 bonding pairs
NH3
Trigonal pyramidal
9
Central atom has 3 domains, one is nonbonding
O3
bent
Trigonal planar
Central atom has 4 domains, 2 are nonbonding
H2O
H O H
Tetrahedral
bent