POLARITY of
MOLECULES Mrs. Analyn A. Vinoya
Physical Science
define what electronegativity is and find its values in the
Define periodic table
Explain explain the VSEPR theory
Learning Draw
Objectives:
draw the geometry of molecules using the VSEPR theory
Distinguish distinguish between polar and non-polar molecules
Relate relate the properties of molecules to its polarity
Electronegativity
Valence electron
Important Dipole
Terms: Covalent bond
Miscible
Immiscible
a. Water + vinegar
b. Water + oil
Activity c. Water + gasoline
d. Oil + vinegar
e. Oil + gasoline
POLAR NONPOLAR
2 factors
that 1) The polarity of the bonds
between atoms which can be
studied based on electronegativity,
determine
the 2) The geometrical shape of the
polarity of
molecule which can be predicted
via the valence shell electron pair
repulsion (VSEPR) theory.
molecules
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.
- occur when electron pairs are unequally
shared. The difference in electronegativity
between atoms is significant.
Polar Examples of compounds having polar
covalent bonds are:
covalent
bonds
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
Elements with the
It creates an electric higher EN value become
dipole. Dipole refers to the partial negative pole
The separation of
“two poles,” meaning while elements with the
charges makes the bond
there is a positive and a lower EN value become
polar
negative pole within a the partial positive pole.
molecule. This makes the molecule
a polar molecule
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 _______________________
1. CH4
2. CF4
Seatwork:
POLAR or 3. O2
NONPOLAR 4. HBr
5. H20
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
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.
Molecular Shape
Guidelines 1. Determine the central
2. Count how many
to
atom of a molecule. The 1 valence electrons the
central atom is the least
central atom has.
electronegative element.
determine 2
the VSEPR
shape of a 3. Count how many
valence electrons the
side atoms have.
molecule:
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.
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.
Solubility, Miscibility, and Polarity
General rule: “like dissolves
like” or “like mixes with like.”
Determine the polarity of the following compounds based on
electronegativity differences and molecular geometry.
Molecular geometry Polarity
• 1. HBr _____________ ___________
• 2. PH3 _____________ ___________
• 3. SiS2 _____________ ___________
• 4. O2 _____________ ___________
• 5. BCl3 _____________ ___________
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
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 ________ ________ ________
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
