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