Slide 1

VSEPR THEORY

11 Important Shapes of VSEPR

Linear Structures2 electron domains, 0 lone pairs

(AX2)

Angle between bonds: 180

Example: BeF2, HCN, andCO2

There are only two places in the valence shell of the central atom of BeF2 where electrons can be found.Repulsion between these pairs of electrons can be minimized by arranging them so that they point in opposite directions.Therefore the VSEPR theory predicts that BeF2 should be a linear molecule, with a 180 angle between the two Be-F bonds.

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Trigonal Planar Structures3 electron domains, o lone pairs

(AX3)Angle between bonds is 120Example: BF3, BH3

There are three places on the central atom in BF3 where valence electrons can be found.Repulsion between these electrons can be minimized by arranging them toward the corner of an equilateral triangle.Therefore this theory predicts the F-B-F bond angle to be 120

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Bent Structures3 electron domains, 2 bonding pairs, 1 lone pairs or 4 electron domains, 2 bonding pairs, 2 lone pairs# of bonding pairs-2# of lone pairs-1Example: NO2 OR # of bonding pairs-2# of lone pairs-2Example: H20

Tetrahedral Structures:(4 electron domains, 0 lone pairs)(AX4)Angle between bonds is ~109.5Example: CH4

Trigonal Pyramidal Structures(4 electron domains, 3 bonding pairs, 1 lone pair)(AX3E)Bond angles are