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1. POLAR AND NON-
POLAR MOLECULES

2. OBJECTIVES:
• Determine if a molecule is polar and
non-polar given its structure.
• Relate the polarity of a molecule to
its properties.

3. POLARITY
• In chemistry, polarity is a separation of
electric charge leading to a molecule or
its chemical groups having an electric
dipole moment, with a negatively charged
end and a positively charged end.

4. Polar and Nonpolar Bonds
• There are two types of covalent bonds
• Nonpolar Covalent Bonds (equal share of electrons)
• Polar Covalent Bonds (unequal share of electrons)

5. Polar Covalent Bond
• A Polar Covalent Bond is unequalsharing of electrons between two
atoms (H-Cl)
• In a polar covalent bond, one atom typically has a negative
charge, and the other atom has a positive charge

6. Nonpolar Covalent Bond
• A Nonpolar Covalent Bond is an equal sharing of electrons between
two atoms (Cl-Cl, N-N, O-O)

8. Classification of Bonds
You can determine the type of bond between two atoms by calculating the
difference in electronegativity values between the elements.
The bigger the electronegativity difference the more polar the bond.
Type of Bond Electronegativity
Difference
Nonpolar Covalent 0  0.4
Polar Covalent 0.5  1.9
Ionic 2.0  4.0

9. Practice
What type of bond is HCl? (H = 2.1, Cl = 3.1)
Difference = 3.1 – 2.1 = 1.0
Therefore it is polar covalent bond.

10. Your Turn To Practice
 N(3.0) and H(2.1)
 H(2.1) and H(2.1)
 Ca(1.0) and Cl(3.0)
 Al(1.5) and Cl(3.0)
 Mg(1.2) and O(3.5)
 H(2.1) and F(4.0)
0.9Polar Covalent
0 Non-Polar Covalent
2.0 Ionic
1.5 Polar Covalent Covalent
2.3 Ionic
1.9 Non-polar Covalent

11. How to show a bond is polar
• Isn’t a whole charge just a partial charge
• d+ means a partially positive (less electronegative)
• d- means a partially negative (more electronegative)
• The Cl pulls harder on the electrons
• The electrons spend more time near the Cl
H Cl
d+ d-

12. Polar Molecules
• Molecules with a positive and a negative end
• Requires two things to be true
 The molecule must contain polar bonds
This can be determined from differences in
electronegativity.
Asymmetric molecule.

13. Asymmetrical Molecules
• If a molecule has polar bonds (and there isno symmetry to cancel out +
and – charges), the molecule is polar.
• Examples:
• H2O HCl
• NH3

14. Symmetrical Molecules
• Because of symmetry, molecules that have polar bonds are overall a
nonpolar molecules (+ and – charges cancel out or balance out)
• Examples:
• CO2 BF3
• CCl4

16. Dipole
When there is unequal sharing of electrons a dipole exists
Dipole is a molecule that has two poles or regions with opposite
charges
A dipole is represented by a dipole
arrow pointing towards the more
negative end

18. Practice Drawing Dipoles
P- Br
P = 2.1
Br = 2.8
P –Br
d+ d-
Practice
 H(2.1) – S(2.5)
 F(4.0) - C(2.5)
 C(2.5) - Si(1.8)
 N(3.0) – O(3.5)

19. The properties of a substance depend in part on it’s
polarity
Polar Compounds
• Stronger intramolecular
forces.
• Form ions when
dissolved in water.
• Higher melting and
boiling points.
• Conduct electricity in
water.
Non-polarCompounds
• Weak intramolecular
forces.
• Do not form ions.
• Lower melting and
boiling points.
• Do not conduct
electricity.

20. “Like dissolves like”
•Polar compounds will dissolved other polar compounds, but
not non-polar compounds.
• Can you think of any examples?

21. Summary
• In a polar bond, one atom is more electronegative than the other.
• In a nonpolar bond, both atoms have similar electronegativities.
• An asymmetric molecule with polar bonds is a polar molecule.
• An asymmetric molecule with nonpolar bonds is a nonpolar molecule.
• A symmetric molecule, regardless of the polarity of the bonds, is
always a nonpolar molecule.

22. ACTIVITY 2
Decide whether the molecules represented by the following
formulas are polar or nonpolar. (You may need to draw Lewis
structures and geometric sketches to do so.)
1. OF2
2. CH2Cl2
3. HCN
4. SO2
5. CH4