Geometry of Molecules
VSEPR Theory
Valence Shell Electron Pair
Repulsion Theory (VSEPR)
The geometry of the molecule at
any
given central
atom
is
determined by the repulsions of
both bonding and nonbonding (lone
pair) electrons in the valence shell.
Hybridization
When atoms join
to form molecules,
the electron
density regions
change.
Hybridization
The process of mixing different
orbitals of the same atom to form a
new set of equivalent orbitals is
termed hybridization.
The shape of the molecule
depends of the number of electron
pairs on the central atom and the
orientation of the hybrid orbitals.
VSEPR
Shapes expected for different
numbers of electron pairs
Two Pairs of Electrons
BeH2
Linear molecule
sp hybrid
There are two pairs of electrons on the
central atom, beryllium.
Linear Molecule
Three Pairs of Electrons
BCl3
Planar triangular, 120o
There are three pairs of
electrons on the central
atom, boron.
sp2 hybrid
Planar Triangular Molecule
Hybrid Orbitals
Four Pairs of Electrons
CH4
Tetrahedral, 109.5o
There are four pairs
of electrons on the
central atom, carbon.
sp3 hybrid
Tetrahedral Molecule
Organic Compounds
A huge number of the compounds that
exist on Earth are carbon-containing
compounds that have the tetrahedral
shape around each carbon atom.
Four Pairs of Electrons
Molecular shapes with four electron
pairs around the central atom.
Five Pairs of Electrons
PCl5
Trigonal bipyramidal
90o and 120o
sp3d hybrid
sp3d and sp3d2
Hybrid Orbitals
Six Pairs of Electrons
SF6
Octahedral, 90o
sp3d2 hybrid
VSEPR Theory
Molecular geometry affects the
characteristics of all compounds.
Learn more with the
VESPR Molecular Model Kit