Molecular Geometry and Bonding Theories
Katherine Shin & Peedith Maldonado
CHAPTER 9
Dedication Page
Our lovely Chemistry teacher,
Ms. Ramona Ricks
=
P.S- Give us an A  Please.
9.1 Molecular Shapes
 The overall shape of a molecule is determined by its
bond angles, the angles made by the lines joining the
nuclei of the atoms in the molecule.
 The possible shapes of Abn molecules depend on the value of
“n.”
 Examples: AB2 molecule must be either linear or bent
AB3 molecule must be either trigonal planar pr trigonal
pyramidal
9.2- The VSEPR Model

A bonding pair of electrons thus defines a region in which the electrons will more
likely be found. (The region is referred to as electron domain)

Nonbonding pair (lone pair) of electrons defines an electron domain that is located
principally on one atom.

THE VSEPR model is based on the idea that electron domains are negatively charged
& therefore, repel each other.
-The VSEPR predicts that the best arrangement of electron domains is the one that
minimizes the repulsions among them.

Electron domain geometry- The arrangement
Of electron domains about the central atom of a
Molecule or ion.
*Molecular geometry is the arrangement of only
the atoms in a molecule or ion.

By looking at the VSEPR model, we can predict
the electron-domain geometry.
-From knowing how many domains are due to
Nonbonding pairs, we can then predict the
Molecular geometry of a molecule or ion from
Its electron-domain geometry.
Electron domain geometries
 There are five….
Molecular Geometry
CO
2
Linear
2 electron domains
Molecular Geometry
Bent
Trigonal
Planar
Trigonal Planar
NO3
BF3
3 electron domains
Molecular Geometry
Trigonal
Pyramidal
Tetrahedral
NH3
CH4
Bent
Tetrahedral
4 electron domains
H2O
Molecular Geometry
Seesaw
Trigonal
Bipyramidal
PCl5
Trigonal
Bipyramidal
T-shaped
5 electron domains
SF4
Linear
ClF3
XeF2
Molecular Geometry
Square
Pyramidal
Octahedral
SF6
Octahedral
6 electron
domains
Square Planar
XeF4
BrF5

9.3 Molecular Shape & Molecular
Polarity
For a molecule that consists of more than two atoms, the dipole moment depends on both the
polarities of the individual bonds and the geometry of the molecule.
Polar
Non-Polar
More Examples
9.5 Hybrid Orbitals

Atomic orbitals on an atom mix to form new orbitals called hybrid orbitals.

The process of mixing atomic orbitals is called hybridization.

Provide a convenient model for using valence-bond theory to describe the covalent
bonds in molecules with geometries that conform to the electron domain
geometries predicted by the VSEPR model.

Steps that allow us to predict the hybrid orbitals used by an atom in the bonding:
1.
Draw the lewis structure for the molecule or ion.
2.
Determine the electron-domain geometry using the VSEPR model.
3.
Specify the hybrid orbitals needed to accommodate the electron pairs based on
their geometric arrangement.
Example:
NH3
QUIZ
Find: molecular formula, electron domain
geometry, molecular geometry, number of electron
domains(bonding/nonbonding), polarity, bond
angles, hybridization
Phosporus hexaflouride
(negative one ion)
PF6
…
P