1. Essential Question: What are polar bonds and polar molecules?
TOPIC: BOND Polarity and Molecule Polarity

2. 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)

3. Polar Covalent Bond
A Polar Covalent Bond is unequal sharing 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

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

6. 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  2.4
Ionic
Above 2.4

7. Practice Your Turn To 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.
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)

8. How to show a bond that is polar
It is NOT 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 d+ d- H Cl

9. Polar Molecules Molecules with a positive and a negative end
Requires two things to be true
1.) The molecule must contain polar bonds
This can be determined from differences in
electronegativity.
2.) Asymmetric molecule.

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

12. Asymmetrical Molecules
If a molecule has polar bonds (and there is no symmetry to cancel out + and – charges), the molecule is polar.
Examples:
H2O HCl
NH3

13. 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

16. Practice Drawing Dipoles
P- Br P = 2.1 Br = 2.8
P –Br
 -
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)

17. Is it Polar? HF
H2O
NH3
CF4
CO2

18. 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.