1. Aim: What are polar bonds and polar molecules?

2. Polar and Nonpolar Bonds
There are two types of covalent bonds
Nonpolar Covalent Bonds (share electrons equally)
Polar Covalent Bonds (share electrons unequally)

3. Polar Covalent Bond
A Polar Covalent Bond is unequal sharing of electrons between two atoms (HCl)
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 (Cl2, N2, O2)

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  1.9
Ionic
2.0  4.0

7. Your Turn To Practice 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 is polar
Isn’t a whole charge just a partial charge
d+ means a partially positive
d- means a partially negative
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
The molecule must contain polar bonds
This can be determined from differences in electronegativity.
Must determine symmetry first.

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