Polarity of Molecules

Mrs. Teresita B. Moreno

Physical Science

Polarity of
Molecules

Week 2_Q3

MELC

•Determine if a

molecule is polar or

non - polar

Objectives

1. differentiate polar and nonpolar
bonds;

2. determine the polarity of chemical
bonds between atoms using the
concept of electronegativity;

3. familiarize with the different shapes
of molecules;

4. explain how polarity of bonds and
molecular geometry affects the
polarity of molecules

Tell whether the compound is an ionic (IC) or
covalent (CC ) based on the type of chemical bond
present
______1. NaCl
______2. CO2
______3. CaCl2
______4. CCl4
______5. Fe2O3

______6. N2O
______7. PCl5
______8. KBr
______9. HCl
______10. AlCl3

IC

CC

IC

CC

IC

CC

CC

IC

CC

IC

Activity 1: Polarity Experiment

Materials:
Water
Vinegar
Oil
Alcohol
6 disposable glasses
spoon

Procedure:
1.
Obtain 6 clean disposable glasses
and prepare the following set-up.

Set-up 1: 1 cup water + 5 tablespoons vinegar
Set-up 2: 1 cup water + 5 tablespoons oil
Set-up 3: 1 cup water + 5 tablespoons alcohol
Set-up 4: 1 cup vinegar + 5 tablespoons oil
Set-up 5: 1 cup vinegar + 5 tablespoons
alcohol
Set-up 6: 5 tablespoon oil + 5 tablespoons

alcohol

2. Thoroughly stir each mixture and observe carefully.
Note: •Do not forget to wash and dry the spoon after each
use.
• Properly label each set-up.
• Samples with oil should first be mixed with dishwashing
liquid before disposing down the sink
Guide Question:
a. Which of the following set-up mixed well? Which did

not?

b. What can you infer from the result of this activity?

• Electronegativity

(EN) measures the
relative tendency
of an atom to
attract electrons
to itself when
chemically
combined with
other atom.

https://images.app.goo.gl/MGHPuB98MGraQLsG6

Table 1. Type of bond based on electronegativity
difference (∆EN) of bonded atoms

Type of Bond

Electronegativity
Difference (∆EN)

Ionic
≥1.7

Polar Covalent
0.5 to 1.6

Nonpolar covalent
≤ 0.4

• Calculate the electronegativity difference and give the type of bond

that exists between the atoms in each of the following pairs.
Molecule

EN of the
first atom

EN of the
second
atom

∆ EN

Type of
Bond

1. CaF2

1.0

4.0

3

ionic

2. Mg Br2

1.2

2.8

1.6

polar
covalent

3. CH4

2.5

2.1

0.4

non polar

4. H2

2.1

2.1

0

non polar

5. NO3

3.0

3.5

0.5

polar

For example, you are asked to predict what type of bond is
present between the following pairs of atoms by determining
their electronegativity difference

1. Ca and Cl
2. Cl and Cl
3. H and Cl
4. S and O
5. C and N

For example, you are asked to predict what type of bond is
present between the following pairs of atoms by determining
their electronegativity difference

1. Ca and Cl
Solution
ENCa = 1.0
ENCl = 3. O
(∆EN) = 1.0 -3.0 = l-2.0 l =2.0
* Ionic bond*

For example, you are asked to predict what type of bond is
present between the following pairs of atoms by determining
their electronegativity difference

2. Cl and Cl
Solution
ENCl = 3.0
ENCl = 3. O
(∆EN) = 3.0 -3.0 = 0

* Nonpolar covalent bond*

For example, you are asked to predict what type of bond is
present between the following pairs of atoms by determining
their electronegativity difference

3. H and Cl
Solution
ENH = 2.1
ENCl = 3. O
(∆EN) = 2.1 -3.0 = l-0.9 l =0.9
* Polar covalent bond*

For example, you are asked to predict what type of bond is
present between the following pairs of atoms by determining
their electronegativity difference

4. S and O
Solution
ENS = 2.5
ENO = 3. 5
(∆EN) = 2.5 -3.5 = l-1.0 l =1.0
* Polar covalent bond*

For example, you are asked to predict what type of bond is
present between the following pairs of atoms by determining
their electronegativity difference

5. C and N
Solution
ENC = 2.5
ENN = 3. 0
(∆EN) = 2.5 -3.0 = l-0.5 l =0.5
* Polar covalent bond*

• A polar covalent

bond is formed when
electrons are shared
unequally by two
atoms in a
compound.

• The bonded pair of

atoms form an
electric dipole
(represented by ).

https://images.app.goo.gl/MeK1MLb8pYqZRwb48

https://images.app.goo.gl/swFedU7Sm1kUTT4Q8

• A nonpolar covalent bond

develops if both atoms
equally share a pair of
electrons between them.

• occurs when the bonding

atoms have
approximately equal EN
value or equal
ability to attract electrons
to each side

B. Polarity of Molecules and Geometry

You can predict the shape or molecular geometry of a substance using the
following steps:

Step 1: Determine the central atom of a molecule. The central atom is the least
electronegative element.

Step 2: Draw the appropriate Lewis dot structure for the molecule.

Step 3: Count the number of bonding pairs of electrons and non-bonding (or
lone pairs) around the central atom.

Step 4: Determine the electron pair orientation using the total number of
electron pairs.

Step 5: Identify the shape of the molecule of based on the location of the atoms.

Different Molecular Shape

https://images.app.goo.gl/8Nnjqw8CwFtR3H6h9

https://images.app.goo.gl/mBMVbfNkDsZwrTQ46

Example:

Example 1:
Predict the molecular geometry of BCl3

• Step 1: ENB = 2.0 ENCl= 3.0

•

Step 3: The central atom has three electron pairs: 3 bonded pairs and no
lone pair

• Step 4: The electron pair orientation for three electrons is trigonal planar.

• 5: The molecular shape of BCl3 is trigonal planar.

Example 2:
Predict the molecular geometry of CO2
• Step 1: ENC= 2.5ENO= 3.0

•

Step 3: For the purpose of determining the position of the bonding pairs, let us
count the double bonds as one bonding pair. Therefore, CO2 has two bonding
pairs of electron.

• 4: The electron pair orientation for two electron pairs is linear.

• Step 5: The molecular shape of CO2 is linear

Example 3:
Predict the molecular geometry of CHCl3.

• Step 1: ENC = 2.5, ENH= 2.1 and ENCl= 3.0. Because carbon is less electronegative

than chlorine and hydrogen is normally terminal atom, C must be the central
atom.

• Step 2:

•

Step 3: There are four bonding electron pairs.

• Step 4: The electron pair orientation for four electron pairs is tetrahedral.

• Step 5: The molecular shape of CHCl3 is linear.

Molecular

Shape