1. Chapter 7.4 – Polar Bonds and Molecules
There are two types of covalent bonds
Nonpolar Covalent Bonds (share equally)
Polar Covalent Bonds (share unequally)

2. Polar Covalent
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

3. Nonpolar Covalent Bond
A Nonpolar Covalent Bond is equal sharing of electrons between two atoms (Cl2, N2, O2)

4. Classification of Bonds
You can determine the type of bond between two atoms by calculating the difference in electronegativity values between the elements
Type of Bond
Electronegativity Difference
Nonpolar Covalent
0  0.3
Polar Covalent
0.3  1.7
Ionic
1.7  3.3

5. 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)

6. Attractions Between Molecules
Besides ionic, metallic, and covalent bonds, there are also attractions between molecules
Intermolecular attractions are weaker than ionic, covalent, and metallic bonds
There are 2 main types of attractions between molecules: Van der Waals and Hydrogen

7. Van der Waals Forces
Van der Waals forces consists of the two weak attractions between molecules
1. dipole interactions – polar molecules attracted to one another
2. dispersion forces – caused by the motion of electrons (weakest of all forces)

8. Hydrogen Bond
Hydrogen Bonds are forces where a hydrogen atom is weakly attracted to an unshared electron pair of another atom

9. Hydrogen Bond
This other atom may be in the same molecule or in a nearby molecule, but always has to include hydrogen
Hydrogen Bonds have about 5% of the strength of an average covalent bond
Hydrogen Bond is the strongest of all intermolecular forces

10. Intermolecular Attractions
A few solids that consist of molecules do not melt until the temperature reaches 1000ºC or higher called network solids (Example: diamond, silicon carbide)
A Network Solid contains atoms that are all covalently bonded to each other
Melting a network solid would require breaking bonds throughout the solid (which is difficult to do)