VSEPR Theory (Molecular Shapes)
A= the central atom, X = an atom bonded to A, E =a lone pair on A
Note: There are lone pairs on X or other atoms, but we don't care. We are interested in only the electron densities or domains around atom A.
Total
Domains
Formula
1
AX
2
AX2
3
Example
Shape
Electron
Geometry
Linear
Linear
H2
2
Linear
Linear
CO,
AXE
1
Linear
Linear
CN
AX
3
Trigonal planar
Trigonal planar
AIBrs
AX,E
2
Bent
Trigonal planar
SnClh
Generic
KY-o
Picture
AX
XAX
Bonded Lone
Atoms
Pairs
1
0
Molecular
AXE,
1
2
Linear
Trigonal planar
AX4
4
0
Tetrahedral
Tetrahedral
SiCL
AX,E
3
1
Trigonal pyramid
Tetrahedral
PH,
AX,Ez
2
2
Bent
Tetrahedral
SeBr2
AXE
1
3
Linear
Tetrahedral
Cl,
Hybridi
Bond
-zation
Angles
180
Sp
180
sp
120
sp
109.5
Total
Generic
Picture
Domains Formnula
5
Bonded Lone
Atoms
Pairs
AX
5
0
AX.E
4
1
AXJE2
Molecular
Electron
Shape
Geometry
Trigonal bipyramid Trigonal bipyramid
See Saw
Trigonal bipyramid
Example
Hybridi
-zation
Bond
Angles
sp°d
90
and
AsFs
SeH
2
T shape
Trigonal bipyramid
ICl3
120
X
6
AX,Es
2
3
Linear
Trigonal bipyramid
BrF2
AX
6
0
Octahedral
Octahedral
SeCle
AX,E
5
1
Square pyramid
Octahedral
IFs
2
Square planar
Octahedral
XeF
AX4E
Notes
sp°a?
90
1. There are no stable AXE4, AX,Ej, AX,E, or AXE, molecules.
2.
All bonds are represented in this table as a line whether the bond is single, double, or triple.
3.
Any atom bonded to thc center atom counts as one domain, even if it is bonded by a double or triple bond. Count atoms and lonc pairs to determinc the
number of domains, do not count bonds.
4. The number of bonded atoms plus lone pairs always adds up to the total number of domains.