4. LEARNING COMPETENCY & CODE:
• Determine if a molecule is polar or non-
polar given its structure (S11/12PS-IIIC-15)
5. •The polarity of molecules is determined by
the two factors:
1) The polarity of the bonds between atoms
which can be studied based on
electronegativity, and
2) The geometrical shape of the molecule
which can be predicted via the valence
shell electron pair repulsion (VSEPR)
theory.
6. ELECTRONEGATIVITY (EN) -
•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
7.
8. For example:
1. Ca and Cl
ENCa = 1.0 (∆EN) = 1.0 – 3.0 = │-2.0│= 2.0 Ionic bond
ENCl = 3.0
2. Cl and Cl
ENCl = 3.0 (∆EN) = 3.0 – 3.0 = 0 Nonpolar covalent bond
ENCl = 3.0
3. H and Cl
ENH = 2.1 (∆EN) = 2.1 – 3.0 = │-0.9│= 0.9 Polar covalent
bond
9. LET’S TRY:
•What type of bond is present between the
following pairs of atoms by determining
their electronegativity difference.
1.S and O
2.C and N
10. ANSWER:
1. ENS= 2.5 (∆EN) = 2.5 – 3.5 = │-1.0│= 1.0 Polar
covalent bond
ENO = 3.5
2. ENC= 2.5 (∆EN) = 2.5 – 3.0 = │-0.5│= 0.5 Polar
covalent bond
ENN = 3.0
11. 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
12. Non-polar covalent bonds
-Occur when electron pairs are shared equally or the
difference in electronegativity between atoms is less
than 0.5.
Examples of substances having non-polar covalent
bonds are:
• H2 EN of H = 2.1 ΔEN = 0.0 Non-
polar molecule
• Cl2 EN of Cl = 3.0 ΔEN = 0.0 Non-
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.
14. 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: Name the shape of based on the location of the
15.
16. Example 1: Predict the molecular geometry of BCl3
• STEP 1: ENB = 2.0 ENCl= 3.0 therefore, B will be the central
atom and three Cl atoms are attached to it. By looking at the
chemical formula, you will also have an idea that Boron will be the
central atom and three atoms of chlorine are attached to it.
• STEP 2:
• 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. STEP 5: The molecular shape of BCl3 is trigonal planar.
17. Example 2: Predict the molecular geometry of CO2
• STEP 1: ENC= 2.5 ENo= 3.0 therefore, C will be the central
atom and two O atoms will be the attached to it. (Use may also use
the chemical formula to predict which atom will be the central
atom
• STEP 2:
•
• 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.
• STEP 4: the electron pair orientation for two electron pairs is
linear.
18. ARE WE MEANT FOR
EACH OTHER OR NOT?
Electronegativity and Molecular
Geometry
19. • The class will be divided into three groups.
• Each group will pick a molecule and determine the polarity of it
based on electronegativity differences and molecular geometry.
• Using the materials, such as manila paper, marker, coloring
materials, ball and stick model, periodic table of elements they will
execute the activity in a collaborative manner.
• After the allotted time, each group will present them out in a creative
way and will be graded according to the following criterion.
Criteria:
Accuracy …………………… 40
Presentation/organization …………………... 30
Creativity …………………… 20
Timeliness …………………… 10
Total 100
20. QUESTIONS FOR DISCUSSION
• What is the central atom of a molecule?
• How do you determine a central atom of a molecule?
• What is electronegativity?
• What is the significance of electronegativity?
• How will you draw the appropriate lewis dot structure of a molecule?
• Why is lewis dot structure important?
• Why is valence shell electron pair repulsion theory or vsepr theory
important?
• How will you determine the polarity of molecules?
• How does understanding of polarity helps you understand your
environment?
• Why there are people who are easy to get along with while others are
21. KEY CONCEPTS:
• Electronegativity (EN) - 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.
• Polar covalent bonds occur when electron pairs are unequally
shared. The difference in electronegativity between atoms is
significant.
• Non-polar covalent bonds occur when electron pairs are shared
equally or the difference in electronegativity between atoms is
less than 0.5.
• Molecular geometry - the Valence Shell Electron Pair Repulsion
22. “Like Dissolves Like” or “Like Mixes With
Like.”
•Cite practical manifestations of
polarity.
23. SOLUBILITY, MISCIBILITY, AND
POLARITY
• Solubility refers to the ability of a solute to dissolve
in a certain amount of solvent.
• Miscibility is the ability of two liquids to mix in all
proportions.
• In the experiment, water, alcohol, and vinegar mixed
because they are both polar substances while oil is a
non-polar substance. Oil and water, oil and vinegar,
and oil and alcohol do not mix because their
