Molecular Geometry

VSEPR and beyond!

Molecular Geometry

Three dimensional arrangment of atoms Molecular polarity determined by

geometry and polarity of bonds Influences forces between molecules Two ideas explain and describe

geometry: VSEPR theory Hybridization

VSEPR

Valence shell electron pair repulsion Repulsion between valence pairs causes

them to be separated as far as possible Separation of electron pairs (and bonds)

creates the geometry of the molecule

VSEPR: Steps

Find the Lewis structure Analyze the structure:

A is central atom B represents atoms bonded to A E represents lone pairs on A

Use Table 6-5 on page 186 to determine geometry

VSEPR Example

Sample Problem 6-5 AlCl

3 Molecule is AB

3, so is trigonal-planar

CBr4

Molecule is AB4, so is tetrahedral

VSEPR Example: Lone Pairs

Only lone pairs on central atom matter! Sample Problem 6-6 Use VSEPR to predict the shape of a

molecule of CO2

AB2, so is linear

ClO3-

AB3E, so is trigonal pyramidal