CK-12-Chemistry Intermediate

http://www.ck12.org Chapter 9. Covalent Bonding

TABLE9.2:(continued)

Number of Electron Pairs

Around Central Atom

Electron Domain Geome-

try

Molecular Geometry Examples

4 tetrahedral tetrahedral CH 4 , NH 4 +

5 trigonal bipyramidal trigonal bipyramidal PCl 5

6 octahedral octahedral SF 6

TABLE9.3: Geometries of Molecules and Ions in Which the Central Atom Has One or More Lone
Pairs

Total Number of

Electron Pairs

Number of

Bonding Pairs

Number of Lone

Pairs

Electron

Domain

Geometry

Molecular

Geometry

Examples

3 2 1 trigonal planar bent O 3

4 3 1 tetrahedral trigonal pyrami-

dal

NH 3

4 2 2 tetrahedral bent H 2 O

5 4 1 trigonal bipyra-

midal

distorted

tetrahedron

(seesaw)

SF 4

5 3 2 trigonal bipyra-

midal

T-shaped ClF 3

5 2 3 trigonal bipyra-

midal

linear I 3 −

6 5 1 octahedral square pyrami-

dal

BrF 5

6 4 2 octahedral square planar XeF 4

Practice with basic molecule shapes at http://phet.colorado.edu/en/simulation/molecule-shapes-basics.

Practice building molecules at http://phet.colorado.edu/en/simulation/build-a-molecule.

Build 3D molecules at http://phet.colorado.edu/en/simulation/molecule-shapes.

Lesson Summary

• Valence shell electron pair repulsion (VSEPR) theory is a technique for predicting the molecular geometry of
  a molecule. A molecule’s shape provides important information that can be used to understand its chemical
  and physical properties.


• According to VSEPR, electron pairs distribute themselves around a central atom in such a way as to maximize
  their distance from each other.


• Electron domain geometries are based on the total number of electron pairs, while molecular geometries
  describe the arrangement of atoms and bonding pairs in a molecule.