OBJECTIVES
Determine
if a molecule is
polar or nonpolar given its
structure (S11/12PSIIIc-15).
the polarity of
the bonds
between the
atoms
2the
geometric
shape of the
molecule
Two main factors determine the
polarity of molecules.
Polar
or
Non polar ?
Electronegativity
is the relative tendency
of an atom to attract
electrons to itself when
chemically combined
with other atoms. The
higher the value of
electronegativity, the
more it tends to pull
electrons toward itself
Atoms and Electronegativity
In a molecule of
chlorine gas
(Cl2), there is
equal sharing of
electrons which
forms a bond
between the two
as in the case of
hydrochloric acid (HCl) in
figure 5, the shared
electron tends to draw
closer to the more
electronegative atom
which is chlorine. This
bond is called polar
covalent bond.
A polar bond has a slightly
negative end labeled with
δ- (sigma), and a slightly
THE DIFFERENCE OF
ELECTRONEGATIVITY BETWEEN THE
ATOMS FORMING A BOND CAN GIVE US
AN INDICATION OF THE POLARITY OF
THE BOND. THE GREATER THE
The bonds between C (2.5) and O (3.5)
in Figure 7 are polar each with an
electronegativity difference of (/2.5 –
3.5/ =) 1.0
The water (H2O)
molecule is another
example of how the
geometry of the
molecule affects its
polarity. While the
bonds between H and
O atoms are polar, its
bent shape points the
The Lewis electron dot diagram
also called electron dot structures are
diagrams that describe the chemical
bonding between atoms in a molecule.
They also display the total number of
lone pairs present in each of the atoms
that constitute the molecule.
Valence Shell Electron Pair
Repulsion (VSEPR) theory
The VSEPR theory- is a guide for us to
predict the arrangement of atoms in a
polyatomic molecule.
In the water (H2O) molecule, the central atom is
oxygen since it is the least numerous element and can
form more bonds than hydrogen.
Create the appropriate Lewis dot structure of the
molecule.
2.
Using the Lewis structure as a guide, determine the
appropriate VSEPR shape for the molecule. The
number of electrons that are shared or bonded
including the lone pairs will help determine the
appropriate VSEPR shape
0
