The document explains the molecular polarity of compounds, distinguishing between polar and nonpolar molecules based on their symmetry and molecular geometry. It discusses intermolecular forces such as van der Waals forces, dipole-dipole attractions, and the significance of electronegativity in determining bond types. Additionally, the text highlights the role of hydrogen bonding in affecting the properties of substances like water and its importance in biological processes.

1. Polar and Nonpolar Molecules
*The Properties Of
Matter Relate To
Their Chemical
Structure

2. •Molecular polarity can be determined by symmetry. Symmetry can
be defined as a balance or regular arrangement of the atoms within
the molecule.
•If a molecule is symmetrical in shape, it is said to be…
•NONPOLAR-----without poles.
•If a molecule is not regular, it is said to be…
•POLAR-----containing (+) and (-) poles.
* POLAR AND NONPOLAR
MOLECULES

3. This called
the Axis of
Symmetry
s line is
* Let’s take a look at some specific
molecules…
Cl-|-Cl We can draw a line down the
middle of this molecule.....
The left side looks like the right. The molecule is symmetrical and is
therefore a NONPOLAR MOLECULE.
The molecule…
H-|-Cl
The left contains Hydrogen and the right contains Chlorine.
Nonsymmetrical and therefore POLAR.

4. H
H H
H
C
POLAR NONPOLAR
Is this a nonpolar or a polar molecule?

5. CH4 is methane gas that we use to
fuel our Bunsen Burners. It is a
very symmetrical molecule and is
therefore a nonpolar molecule.

6. H
H
O
POLAR NONPOLAR
Is this molecule nonpolar or polar?

7. Water molecules are angular in shape
due to the two bonded hydrogen and
the two unbounded pairs of electrons
on the oxygen. This angular shape,
along with the electronegativity of the
oxygen, causes the molecule to be
polar.

8. O=C=O
POLAR NONPOLAR
Is this molecule nonpolar or polar?

9. This molecule is symmetrical
Carbon dioxide has two
double covalent bonds that
form a linear molecule. It is
very symmetrical and
therefore nonpolar.

10. H
H
N
H
Polar or nonpolar, that is the question?

11. Ammonia has a trigonal pyramidal
shape due to the unbounded pair of
electrons on the nitrogen. It has
definite polar characteristics
because it is not totally
symmetrical. Yet it is not as strong
of a polar bond as water due to the
lower electronegativity of the
nitrogen atom.

12. SYMMETRICAL
NONPLOAR
POLAR
N S
ON
M
YM
E
I
C
TR
A
L

13. *Van der
Waals forces
*Van der Waals forces' is a general term used
to define the attraction of intermolecular
forces between molecules. There are two
kinds of Van der Waals forces: weak London
Dispersion Forces and stronger dipole-dipole

14. *Molecules that are polar
are also said to be
dipoles. Di- means 2. –
pole means it has (+)
and (-) electrostatic
poles. Thus the name
DIPOLE.

15. *Because dipoles have charged
ends, they can attract each
other. This is called…
DIPOLE-DIPOLE ATTRACTION.

16. Because dipoles have charged ends, they
can attract each other. This is called
Dipole-dipole attraction. The stronger
the dipoles, the stronger the force of
attraction.
Because a dipole has charged ends, it
can attract the ions in an ionic
compound also. This is called the ion-
dipole attraction.

17. *London Dispersion
Forces
At any instant in time, the electrons in a particle may be unequally distributed.
This means one side of the molecule will have a charge for just an instant.
This slight charge will affect the neighboring molecule and force that
molecules electrons into an unequal pattern as well.
This produces a slight attraction between the molecules.

18. *London Dispersion
Forces
*The slight attraction between molecules can then
affect the other molecules near them.
*This is the weakest force of the Van der Waal’s
forces.
*This weak force can be increased by an increase in
the number of electrons.
*This weak force will be decreased if the molecules
are further apart.

19. *Molecular geometry is the three-dimensional arrangement of the atoms
that constitute a molecule. It determines several properties of a substance
including its reactivity, polarity, phase of matter, color, magnetism and
biological activity.
*Molecules is an electrically neutral group of two or more atoms held
together by chemical bonds. Molecules are distinguished from ions by their
lack of electrical charge.
*Ionic bond when the bond occurs between metal and nonmetal. Oppositely
charged ions are held together by electrostatic attraction.
*Covalent bond when bond occurs between non metals. Neutral atoms
share electrons equally between them.
*Polar covalent bond Partially charged atom are held together by unequally
charged electron. The ability of an atom to attract electrons in the presence
of another atom is a measurable property called electronegativity.
Geometry Of Molecules

20. *Comparison of an ionic bond
and a covalent bond

21. Electronegativity is a measure of the ability of an atom in a molecule to
draw bonding electrons to itself. The most commonly used scale of
electronegativity is that developed by Linus Pauling in which the value
4.0 is assigned to fluorine, the most electronegative element. Cesium
and francium which are the least electronegative at 0.7
The bond between the atom whose difference in
electronegativities is less than 0.5 it is considered
be Nonpolar.
if the electronegativity is in between 0.5 to 2.0 it is
considered as Polar covalent. And lastly if the
electronegativity in between two atom is 2.0 or m
it is considered as Ionic bond.

22. Ionic bond

23. Polar Covalent Bond
Valence Electrons. The electrons in the outermost shell are the valence
electrons the electrons on an atom that can be gained or lost in a chemical
reaction.

24. *HYDROGEN
Compounds such as water and ammonia have hydrogen
atoms that are bonded to smaller atoms of relatively high
electronegativity.
When hydrogen atoms are joined in a polar covalent bond with
a small atom of high electronegativity such as O, F or N, the
partial positive charge on the hydrogen is highly concentrated
because of its small size. If the hydrogen is close to another
oxygen, fluorine or nitrogen in another molecule, then there is
a force of attraction termed a dipole-dipole interaction.
Hydrogen bonding has a very important effect on the
properties of water and ice. Hydrogen bonding is also very
important in proteins and nucleic acids and therefore in life
processes.

25. *HYDROGEN BONDING
Notice how the water molecules are attracted to each other. This is an
example of hydrogen bonding.

26. *MORE POWER
The fluorine atom has a higher electronegativity (a greater attraction for an
electron) than an oxygen atom. Therefore the electrons in an H-F bond are
pulled closer to the fluorine and this makes the hydrogen bond between H-F
molecules stronger.

27. *Polarity Related To Properties Of