VSEPR Theory
Chemistry MYP
Ms. Khan
VSEPR Theory
▪ VSEPR – valence shell electron pair repulsion
– repulsion between sets of valence electrons surrounding an
atom causes them to be as far apart as possible
▪ electron domain – region where electrons exist
bonded pair domains
lone pair domains
single bond = 1 domain
1 pair = 1 domain
double bond = 1 domain
2 pairs = 2 domains
triple bond = 1 domain
3 pairs = 3 domains
VSEPR Theory
▪ electron domain geometry (EDG) – three dimensional
arrangement of all domains (bonded pair and lone pair)
▪ molecular domain geometry (MDG) – three dimensional
arrangement of bonded pair domains
– if all domains are bonded pairs, the EDG and MDG will be
the same
▪ bond angle – angle between bonded pair domains
– lone pairs sit directly on the atom and have greater
repulsion, cause bond angle to decrease slightly
VSEPR Theory
geometry notation
perspective notation
▪ A = central atom
(indicates position of domain)
▪ X = peripheral atom
▪ ––– = in the plane
▪ E = lone pair on central
atom
▪
= in front of the plane
▪
= behind the plane
Geometry of 2 Domains
AX2
ex: HCN
– 2 bonded pair domains
– 0 lone pair domains
▪ EDG: linear
▪ MDG: linear
▪ bond angle: 180°
X
A
X
Geometry of 3 Domains
AX3
ex: CO32– 3 bonded pair domains
– 0 lone pair domains
X
▪ EDG: trigonal planar
▪ MDG: trigonal planar
▪ bond angle: 120°
A
X
X
Geometry of 3 Domains
AX2E
ex: CCl2
– 2 bonded pair domains
– 1 lone pair domains
..
▪ EDG: trigonal planar
▪ MDG: bent
▪ bond angle: <120°
A
X
X
Geometry of 4 Domains
AX4
ex: PO43– 4 bonded pair domains
– 0 lone pair domains
X
▪ EDG: tetrahedral
▪ MDG: tetrahedral
▪ bond angle: 109.5°
A
X
X
X
Geometry of 4 Domains
AX3E
ex: PF3
– 3 bonded pair domains
– 1 lone pair domains
..
▪ EDG: tetrahedral
▪ MDG: trigonal pyramidal
▪ bond angle: <109.5°
A
X
X
X
Geometry of 4 Domains
AX2E2
ex: H2O
– 2 bonded pair domains
– 2 lone pair domains
X
▪ EDG: tetrahedral
▪ bond angle: <109.5°
..
▪ MDG: bent
A
X
Geometry of 5 Domains
AX5
ex: PCl5
– 5 bonded pair domains
– 0 lone pair domains
▪ EDG: trigonal bipyramidal
▪ MDG: trigonal bipyramidal
X
X
A
X
▪ bond angle: 90°, 120°
two types of positions:
2 axial, 3 equatorial
X
X
Geometry of 5 Domains
AX4E
ex: SF4
– 4 bonded pair domains
– 1 lone pair domains
▪ MDG: seesaw
A
..
▪ EDG: trigonal bipyramidal
X
X
▪ bond angle: <90°, <120°
lone pairs fill equatorial
positions
X
X
Geometry of 5 Domains
AX3E2
ex: BrF3
– 3 bonded pair domains
– 2 lone pair domains
▪ EDG: trigonal bipyramidal
▪ MDG: T-shaped
X
X
A
▪ bond angle: <90°
lone pairs fill equatorial
positions
X
Geometry of 5 Domains
AX2E3
ex: XeCl2
– 2 bonded pair domains
– 3 lone pair domains
▪ MDG: linear
A
..
▪ EDG: trigonal bipyramidal
X
▪ bond angle: 180°
lone pairs fill equatorial
positions
X
Geometry of 6 Domains
AX6
ex: PF61– 6 bonded pair domains
– 0 lone pair domains
▪ EDG: octahedral
▪ MDG: octahedral
▪ bond angle: 90°
X
X
A
X
X
X
X
Geometry of 6 Domains
AX5E
ex: XeOF4
– 5 bonded pair domains
– 1 lone pair domains
▪ EDG: octahedral
▪ MDG: square pyramidal
▪ bond angle: <90°
X
X
X
A
..
X
X
Geometry of 6 Domains
AX4E2
ex: ICl41– 4 bonded pair domains
– 2 lone pair domains
▪ EDG: octahedral
▪ MDG: square planar
▪ bond angle: 90°
X
X
..
A
..
X
X