This document discusses the polarity of molecules. It defines electronegativity and the VSEPR theory for determining molecular geometry. A molecule's polarity depends on the polarity of its bonds, determined by electronegativity differences, and its geometry. Polar bonds result from unequal sharing of electron pairs between different elements. Molecular geometry is predicted using VSEPR theory to minimize electron pair repulsion. Both factors, bond polarity and geometry, must be considered to classify a molecule as polar or nonpolar. Examples are provided to demonstrate how to determine a molecule's polarity.

1. POLARITY of
MOLECULES Mrs. Analyn A. Vinoya
Physical Science

2. Learning
Objectives:
define what electronegativity is and find its values in the
periodic table
Define
explain the VSEPR theory
Explain
draw the geometry of molecules using the VSEPR theory
Draw
distinguish between polar and non-polar molecules
Distinguish
relate the properties of molecules to its polarity
Relate

3. Important
Terms:
Electronegativity
Valence electron
Dipole
Covalent bond
Miscible
Immiscible

4. Activity
a. Water + vinegar
b. Water + oil
c. Water + gasoline
d. Oil + vinegar
e. Oil + gasoline

5. POLAR NONPOLA
R

6. 2 factors
that
determine
the
polarity of
molecules
1) The polarity of the bonds
between atoms which can be
studied based on
electronegativity,
2) The geometrical shape of the
molecule which can be predicted
via the valence shell electron pair
repulsion (VSEPR) theory.

7. Electronegativity
measure of the relative
tendency of an atom to attract
electrons to itself when
chemically combined with
another atom. The higher the
value of electronegativity, the
more it tends to attract
electrons toward itself.

8. Polar
covalent
bonds
- occur when electron pairs are unequally
shared. The difference in electronegativity
between atoms is significant.
Examples of compounds having polar
covalent bonds are:
HCl EN of H = 2.1 EN of Cl = 3.0 ΔEN =
0.9
HF EN of H = 2.1 EN of F = 4.0 ΔEN = 1.9

9. The separation of charges
makes the bond polar
It creates an electric
dipole. Dipole refers to
“two poles,” meaning there
is a positive and a
negative pole within a
molecule.
Elements with the
higher EN value become
the partial negative pole
while elements with the
lower EN value become
the partial positive pole.
This makes the molecule a
polar molecule

10. Identify which of the following are polar or
nonpolar molecules:
1. H2 EN of H = 2.1 _____________________
2. Cl2 EN of Cl = 3.0 ____________________
3. F2 EN of F = 4.0 _____________________
4. HI EN of H = 2.1 _______________________

11. Seatwork:
POLAR or
NONPOLAR
1.
CH4
2. CF4
3. O2
4. HBr
5. H20

12. Answer key
1.CH4
EN of H = 2.1 EN of C = 2.5 ΔEN = 0.4 Non polar covalent
2.CF4
EN of C = 2.5 EN of F = 4.0 ΔEN = 1.5 Polar covalent
3. O2
EN of O = 3.4 ΔEN = 0.0 Non polar covalent bond
4. HBr
EN of H= 2.1 EN of Br = 2.8 ΔEN = 0.7 Polar covalent
bond

13. Molecular Geometry
The valence shell electron pair repulsion
theory or VSEPR theory
helps predict the spatial arrangement of atoms in a polyatomic
molecule. The shapes are designed to minimize the repulsion within
a molecule.

15. Molecular Shape

16. Guidelines
to
determine
the VSEPR
shape of a
molecule:
1
1. Determine the central
atom of a molecule. The
central atom is the least
electronegative element.
2
2. Count how many
valence electrons the
central atom has.
3. Count how many
valence electrons the
side atoms have.

17. 4. Create the appropriate Lewis
structure of the molecule.
5. Using the Lewis structure as a guide,
determine the appropriate VSEPR
shape for the molecule.
6. Note how many electrons are shared
and unshared. This will help determine
the appropriate VSEPR shape.

20. CO2; wherein the
electronegativity difference of C
and O is 1.0 which makes the
bond between them polar.
However, carbon is placed in
the middle of two oxygen
atoms making the molecular
structure linear. This equal
distribution of polar bonds
make the molecule non-polar.

21. Solubility, Miscibility, and Polarity
General rule: “like dissolves
like” or “like mixes with like.”

22. Determine the polarity of the following compounds based on
electronegativity differences and molecular geometry.
Molecular geometry Polarity
• 1.
HBr _____________ ___________
• 2.
PH3 _____________ ___________
• 3.
SiS2 _____________ ___________
• 4.

23. Determine the polarity of the following
compounds based on electronegativity
differences and molecular geometry.
Molecular geometry Polarity
• 1. HBr linear polar
• 2. PH3 trigonal pyramidal polar
• 3. SiS2 linear non-polar
• 4. O2 linear non-polar
• 5. BCl3 trigonal planar non-polar

24. EVALUATION:
Determine the following: (Bond Polarity, Molecular
Geometry and Polarity of Molecule)
Bond Molecular Polarity of
Polarity Geometry Molecule
• a. H2O ________ ________ ________
• b. CCl4 ________ ________ ________
• c. BF3 ________ ________ ________
• d. SF6 ________ ________ ________
• e. SiF4 ________ ________ ________

25. EVALUATION:
Bond Polarity Molecular Geometry Polarity of Molecule
• a. H2O polar bent polar
• b. CCl4 non-polar tetrahedral non-polar
• c. BF3 polar trigonal planar non-polar
• d. SF6 polar octahedral non-polar
• e. SiF4 polar tetrahedral non- polar