1. Polarity of Covalent Bonds

2. Covalent bonds share electrons
(ionic bonds transfer electrons)
Bonding electrons (shared pairs of
electrons between elements) are pulled
on (like in a tug-of-war) as atoms
compete for the electrons

3. Electronegativity Values
Refer to p. 161 in your textbook

4. Polar Molecules
A polar molecule is created when electrons are shared unequally in a molecule.
The electrons are held closer to the more electronegative atom than they are to the less electronegative atom
This causes part of the molecule to be slightly negative, and the other part to be slightly positive.

5. Electronegativity Determines Polarity
Each atom has an electronegativity value which corresponds to how strongly it attracts electrons.
Polarity is determined by the difference in the electronegativity values of atoms that make up a molecular compound.

6. Determining Polarity…
Step 1: Find the electronegativity values of the atoms that make up the molecule (look at an electronegativity table, p. 161 in your textbook) Step 2: SUBTRACT the value of the less electronegative atom from the value of the more electronegative atom.

7. Non-polar covalent difference = 0.0 – 0.3 Polar Covalent
Ionic
difference > 1.7
Polar-covalent

8. HCl H – Cl for example… electronegativity 2.1 3.0 value
difference , a POLAR covalent molecule
**Chlorine is stronger than H (3.0>2.1) and therefore pulls the shared electrons closer to the Cl atom, inducing a negative charge at its pole – H therefore acquires a positive charge, hence, a POLAR molecule
+H :Cl -