• I can describe the VSEPR theory• I can determine the VSEPR model of a given

molecule• I can predict the shape of a molecule using

VSEPR theory

Learning Targets

• The properties of molecules depend not only on the type of bonding but also on molecular geometry or the shape of the molecule.

• There are two theories used to predict molecular geometry: VSEPR theory (we will discuss) and hybridization (we will not discuss)

Molecular Geometry

• VSEPR – Valence Shell Electron Pair Repulsion• Theory is used to predict the shape of

molecules. • This theory is based on the idea that pairs of

electrons surrounding an atom repel each other causing the electron pairs to be as far apart from each other as possible.

VSEPR Theory

• The Lewis structure is used to determine the VSEPR model of the molecule.

• The following symbols are used for the VSEPR model

VSEPR Theory

A Central Atom

B Bonded Atom

E Lone Pair

Symbols

• The VSEPR model is used to determine the geometry and bond angles of the molecule

VSEPR Models

VSEPR Model Geometry Bond Angle

AB Linear 180o

AB2 Linear 180o

AB2E Bent 120o

AB3 Trigonal Planar 120o

AB2E2 Bent 105o

AB3E Trigonal Pyramidal 107o

AB4 Tetrahedral 109.5o

Other VSEPR Models

VSEPR Model Geometry

AB5 Trigonal Bypyramidal

AB4E Seesaw

AB3E2 T-Shaped

AB6 Octahedral

AB5E Square Pyramidal

AB4E2 Square Planar

AB5 Trigonal Bypyramidal

VSEPR Models

• Phosphorus Trichloride

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

• PCl3

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

• PCl3

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

P ClCl

Cl..

.

.

.

...

. .

. .

. . . .

. .

. .

• PCl3

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

P ClCl

Cl..

.

.

.

...

. .

. .

. . . .

. .

. .

VSEPR Model: AB3E

• PCl3

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

P ClCl

Cl..

.

.

.

...

. .

. .

. . . .

. .

. .

VSEPR Model: AB3E

Geometry: Trigonal Pyramidal

• CH2Cl2

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

• CH2Cl2

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

C ClCl

H..

.

.

. .

. . . .

. .

H

• CH2Cl2

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

C ClCl

H..

.

.

. .

. . . .

. .

HVSEPR Model: AB4

• CH2Cl2

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

C ClCl

H..

.

.

. .

. . . .

. .

HVSEPR Model: AB4

Geometry: Tetrahedral

• CO2

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

• CO2

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

C OO. . . .

. .. .

• CO2

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

C OO. . . .

. .. .

VSEPR Model: AB2

• CO2

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

C OO. . . .

. .. .

VSEPR Model: AB2

Geometry: Linear

• HCN

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

• HCN

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

C NH . .

• HCN

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

C NH . .

VSEPR Model: AB2

• HCN

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

C NH . .

VSEPR Model: AB2

Geometry: Linear

• Nitrite Ion

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

• NO2–

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

• NO2–

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

N OO. . . .

. .. .

. .

. .

• NO2–

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

VSEPR Model: AB2E

N OO. . . .

. .. .

. .

. .

• NO2–

Practice ProblemsDetermine the VSEPR model and geometry for each of the following molecules.

VSEPR Model: AB2E

Geometry: Bent

N OO. . . .

. .. .

. .

. .