A chemical formula tells us
The identity of atoms
The number of atoms
The Lewis structure tells us
The identity of atoms
The number of atoms
How the atoms and electrons are arranged
The molecular geometry tells us
The identity of atoms
The number of atoms
How the atoms and electrons are arranged
The 3-D shape of that atom arrangement
VSEPR Model
A model used to sort out how the bonding and nonbonding electrons orient themselves in three dimensions
What does VSEPR stand for?
Valance
Shell
Electron
Pair
Repulsion
In the model, pairs of electrons arrange themselves
To get as far away from each other as possible
Why do they do this?
In order to minimize their negative repulsions
Electron Domain
A region around a central atom where electrons are likely to be located
Bonding pair
A pair of electrons between two nuclei
Unshared pair
(Also called nonbonding pair or lone pair)
A pair of electrons
Multiple bonds
Double or triple bonds make up a single domain
Linear
2 domains
Angle: 180*
Trigonal Planar
3 domains
Angles: 120*
Tetrahedral
4 domains
Angles: 109.5*
Trigonal bipyramidal
5 domains
Angles: 120
, 90
, 180*
Octahedral
6 domains
Angles: 90*
Five Fundamental Electron Domain Arrangements
Linear
Trigonal-planar
Tetrahedral
Trigonal-bipyramidal
Octahedral
Linear molecule
(AB2)
2 electron domains (Linear domains)
0 nonbonding domains
Bond Angles: 180*
Linear Molecule Examples
CO2
SCN-
C2H2
Trigonal Planar Molecule
(AB3)
3 electron domains
(trigonal planar)
0 nonbonding domains
Bond Angles: 120*
Trigonal Planar Molecule Examples
BF3
CH2O
NO30
(CH3)2CO
Bent Molecule
(AB2)
3 electron domains
(Trigonal planar)
1 nonbonding domain
Bond Angles: 120*
Bent Molecule Examples
O3
NO2-
Tetrahedral Molecule
(AB4)
4 electron domains
(Tetrahedral)
0 nonbonding domain
Bond Angles: 109.5*
Tetrahedral Molecule Examples
CH4
CF2H2
Trigonal Pyramidal Molecule
(AB3)
4 electron domains
(Tetrahedral)
1 nonbonding domain
Bond Angles: 109.5*
Trigonal Pyramidal Molecule Examples
H20
CH3OH
Bent Molecule
(AB2)
4 electron domains
(Tetrahedral)
2 nonbonding domain
Bond Angles: 109.5*
Bent Molecule Examples
H2O
CH3OH
Unshared pairs take
Up more space than bonding pairs
Multiple bonds bulge and
Take up more space
Trigonal Bi-Pyramidal Molecule
(AB5)
5 electron domains
(Trigonal by-pyramidal)
0 nonbonding domain
Bond Angles: 90
, 120
, 180*
Trigonal Bi-Pyramidal Molecule Examples
PCl5
See Saw Molecule
5 electron domains
(Trigonal bi-pyramidal)
1 nonbonding domain
Bond Angles: <90
, <120
, 180*
See Saw Molecule Examples
SF4
Equatorial
Always the _____ position
Unshared
The ___pair takes up more space
Unshared
Repulsion forces are minimized if the ____ pair is in the equatorial position
T-Shape Molecule
(AB2)
5 electron domains
(Trigonal bi-pyramidal)
2 nonbonding domains
Bond Angles: <90
, 180
T-Shape Molecule Example
ClF3
Linear Molecule
(AB2)
5 electron domains
(Trigonal bi-pyramidal)
3 nonbonding domains
Bond Angles: 180*
Linear Molecule Example
XeF2
I3-1
Octahedral Molecule
6 electron domains
(Octahedral)
0 nonbonding domain
Bond Angles: 90
, 180
Octahedral Molecule Example
SF6
Square Pyramidal Molecule
6 electron domains
(Octahedral)
1 nonbonding domain
Bond Angles: <90*
Square Pyramidal Molecule Example
BrF5
Square Planar Molecule
(AB4)
6 electron domains
(Octahedral)
2 nonbonding domains
Bond Angles: 90
, 180
Square Planar Molecule Example
XeF4