Molecular Geometry(VSEPR theory)

Prem D. SattsangiChristopher L. Byers (programmer)

© 2010

Learning Molecular Geometry

The total number of bonds and unshared (non- bonded) electron pairs (E.P.) determine the electron domain around the central atom.

Bonds will be shown as solid lines.

Non-Bonded E.P. will be shown as balloons.

O

H H

E.G.

Trigonal Planar StructuresA = Central AtomX = Bonded Atom (or Non-Bonded E.P.)120° angles, sp2 hybridization

Molecular Geometry“Bent”

X

A

X

120°

X

A

X X

Molecular Geometry“Trigonal Planar”

AX

XX 120°

Top Views

Side View

In molecular geometry the orbitals are not shown.

Aluminum chloride AlCl3

Nitrate Ion NO3-

Nitrite Ion NO2-

Tetrahedral StructuresX

X

AX109.5°

A = Central AtomX = Bonded Atom (or Non-Bonded E.P.)109.5° angles, sp3 hybridization

Molecular Geometry“Trigonal Pyramidal”

Molecular Geometry“Bent”

X

X

AX X

107°

X

AX104.5°

Each Non-Bonded E.P. reduces the angle by 2.5°.

Methane CH4

Ammonia NH3

Water H2O

Trigonal Bipyramidal StructuresX

X

AX

XX 120°

90°

Axial

Equatorial

A = Central AtomX = Bonded Atom (or Non-Bonded E.P.)90° angle between Axial and Equatorial bonds120° angle between Equatorial bonds, sp3d hybridization

X

X

AX

X

Molecular Geometry“Seesaw”

Molecular Geometry“T-Shaped”

X

X

A

Molecular Geometry“Linear”

X

X

AX

The non-bonded E.P. occupies the equatorial position.

Phosphorus pentachloride PCl5

Sulfur tetrafluoride SF4

Chlorine trifluoride ClF3

Octahedral Structures

90°

A = Central AtomX = Bonded Atom (or Non-Bonded E.P.)90° angles, sp3d2 hybridization

Molecular Geometry“Square Pyramidal”

Molecular Geometry“Square Planar”

X

X

X

A

X

X

X

X

X

A

X

X90°

X

XA

X

X90°

X

Sulfur hexafluoride SF6

Bromine pentafluoride BrF5

Review Quiz 1Name the molecular geometry of the following compounds.

NO O

NO2

H

NH H

NH3

Trigonal Planar Tetrahedral

Trigonal PyramidalBent

OH H

H2O

Bent

F

BF F

BF3 sp2 hybrid

H

H

CH HCH4 sp3 hybrid

Review Quiz 2Name the molecular geometry of the following compounds.

Cl

Cl

PCl

ClCl

PCl5sp3d hybrid

Trigonal Bipyramidal Seesaw

Linear

F

F

SF

F

SF4

T-Shaped

F

F

Xe

XeF2F

F

ClF

ClF3

Review Quiz 3Name the molecular geometry of the following compounds.

F

F

F

S

F

F

F

SF6

sp3d2 hybridF

F

Br

F

F

F

BrF5

FXe

F

F

F

XeF4

Octahedral Square Pyramidal Square Planar

Trigonal Bipyramidal (has 5 electron domains)

# Bonds Non-Bond E.P. Geom.

5 0 Trig. Bipyr

4 1 Seesaw

3 2 T-Shaped

2 3 LinearCl

P

Cl

Cl

Cl

Cl

F

F

F

Cl

F

F

Xe

F

FF

F

S