VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) Theory

Electron groups - lone pairs, single bonds, multiple bonds, single electrons - repel one another through coulombic forces.

- electron groups attracted to nucleus

- maximum separation = best

Linear Geometry

- 2 electron groups (2 single bonds)

- 180 degree bond angle

- EX: CO2

Trigonal Planar Geometry

- 3 electron groups

- 120 degree bond angles

- EX: BF3

Tetrahedral Geometry

- 4 electron groups

- three dimensional

- 109.5 degree bond angles

- EX: CH4, methane

Trigonal Bipyramidal Geometry

- 5 electron groups

- 3 groups on flat plane (120 degrees)

- 2 above/below axial positions (90 degrees)

- Angles differentiate

- EX: PCl5

Octahedral Geometry

- 6 electron groups

- 4 groups lie on flat plane

- 2 above/below axial positions

- All angles are 90 degrees

electron geometry

the geometrical arrangement of the ELECTRON groups

molecular geometry

the geometrical arrangement of the atoms

bent / v-shaped molecular geometry

- trigonal planar derivative

- 120 degree bond angles

- 2 outer atoms, 1 lone pair

trigonal pyramidal molecular geometry

- tetrahedral derivative

- 4 electron groups

- 1 lone pair of electrons

- 3 bonding pairs

- less than 109.5 degree bond angles

- EX: NH3 107 degree

Bent molecular geometry

- tetrahedral derivative

- 4 electron groups

- 2 lone pairs of electrons

- 2 bonding pairs

- EX: H20, 104.5 degree

effect of lone pairs on molecular geometry

the more lone pairs, the more repulsion, the smaller bond angle

see-saw molecular geometry

- trigonal bipyramidal derivative

- 5 electron groups

- 1/5

- 4 bonding pairs, 1 lone pair

- lone pair occupies equatorial position

- 2 90 degree bond pair repulsions

- EX: SF4

T-Shaped molecular geometry (5)

- trigonal bipyramidal derivative

- 5 electron groups

- 2/5

- 3 bonding pairs, 2 lone pairs

- bond angles 90 degrees

- EX: BrF3

Linear molecular geometry

- trigonal bipyramidal derivative

- 5 electron groups

- 3/5

- 2 bonding, 3 lone pairs

- 180 degrees

- E: XeF2

Square Pyramidal molecular geometry

- octahedral derivative

- 1/6

- one lone pair

- 90 degree bond angles

Square Planar molecular geometry

- octahedral derivative

- 2/6

- 2 lone pairs

- 90 degree bond angles

T-Shaped molecular geometry (6)

- octahedral derivative

- 3/6

- 3 lone pairs

- 90 degree bond angles

Linear molecular geometry (5)

- octahedral derivative

- 4/6

- 4 lone pairs

- 2 bonding, 4 lone pairs

- 180 degree bond angles