Molecular Geometry - Hybridization
VSEPR - Valence shell electron pair repulsion
(electron pairs will go as far apart in space as they can)
1. Draw Lewis Structure
2. Count number of electron groups around central atom (a multiple bond is “one” electron group) E
3. Choose electron group geometry based on 2,3,4,5 or 6 groups around the central atom
4. For molecular geometry look only at where the atoms are placed, lone pairs are “invisible”
5. For hybridization, count the number of lone pairs and sigma bonds to find out number of molecular orbitals needed. Count
only 1 bond from a double or triple bond as sigma.
2 orbitals = sp 3 orbitals = sp2 4 orbitals = sp3 5 orbitals = sp3d 6 orbitals = sp3d2
6. For 3D drawing, use Lewis structure and place atoms and lone pairs in the locations around central atom appropriately. For
5 trigonal bipyramidal, lone pairs go on corners of triangle (equatorial positions). For 6 octahedral, lone pairs go above and
below the plane (axial positions) and not on the 4 corners of the middle square.
# e- groups
around
central atom
e- group geometry
Example
2
linear
3
Trigonal planar
Lewis Structure
# lone
pairs
Geometry
designation
Molecular shape
hybridization
CO2
0
AX2
Linear
sp
BF3
0
AX3
Trigonal planar
sp2
NO3-
0
AX3
3
Trigonal planar
NO2-
1
AX2E
Bent
sp2
4
tetrahedral
CH4
0
AX4
tetrahedral
sp3
3D model
4
tetrahedral
NH3
1
AX3E
Trigonal
pyramidal
sp3
4
tetrahedral
H2O
2
AX2E2
bent
sp3
5
Trigonal bipyramidal
PCl5
0
AX5
Trigonal
bipyramidal
sp3d
5
Trigonal bipyramidal
SF4
1
AX4E
Seesaw
sp3d
5
Trigonal bipyramidal
ClF3
2
AX3E2
T-shape
sp3d
BrF3
5
Trigonal bipyramidal
XeF2
3
AX2E3
linear
sp3d
6
octahedral
SF6
0
AX6
octahedral
sp3d2
6
octahedral
ClF5
1
AX5E1
Square
pyramidal
sp3d2
6
octahedral
ICl4-
2
AX4E2
Square planar
sp3d2
XeF4