1. Polar Bonds and Molecules
Covalent Bonding
Polar Bonds and Molecules

2. Covalent Bonding -- Polar Bonds and Molecules --
Bond Polarity
“The Tug of War”
The pairs of electrons that are bonds between atoms are pulled between the nuclei of the atoms in a bond.
The electronegativities of the atoms determine the winner.
Classifications for Bonds
Nonpolar covalent
When atoms pull the bond equally
Happens with two atoms of equal electronegativity, most often using the same atoms
Examples: H2, O2, N2
Polar covalent
When atoms pull the bond unequally
Happens with two atoms of different electronegativities
Example: HCl, HF, NH

3. Covalent Bonding -- Polar Bonds and Molecules --
Bond Polarity
In a polar molecule, one end of the molecule is slightly more electronegative than the other atom, resulting in one atom being slightly negative (-) because of higher electronegativitiy, and the other atom being slightly positive (+) because of lower electronegativity.
 is known as a partial charge since it is much less than 1+ or 1- charge.

4. Covalent Bonding -- Polar Bonds and Molecules --
Bond Polarity
Electronegativities and Bond Types
H: Cl: Since hydrogen is less, it will have the positive partial charge while chlorine has the negative partial charge.
3.0 – 2.1 = 0.9 HCl is polar covalent.
0.0 – 0.1 difference
Nonpolar covalent bond
H – H (0.0 difference)
0.1 – 1.7 difference
Polar covalent bond
H – Cl (0.9 difference)
1.7 + difference
Ionic bond
Na+Cl- (2.1 difference)

5. Covalent Bonding -- Polar Bonds and Molecules --
Polar Molecules
Dipole
Molecule that has two poles
Example: HCl from the previous page
Polar vs. Nonpolar
H2O and CO2
Both have 3 atoms; yet,
One is polar and one is nonpolar.
Why?
Structure (with bond polarity) determines the molecules polarity.

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