Polar Bonds and Molecules Notes

Bond Polarity

• The bonding pairs of electrons are pulled in a tug-of-war between the nuclei of the atoms sharing the electrons.

• When the atoms pull evenly, the bonding electrons are shared evenly and the bond is a nonpolar covalent bond.

• Examples: diatomic oxygen, nitrogen, and chlorine.

• When covalent bonds join two atoms of different elements and the bonding electrons are not shared equally, the bond is a polar covalent bond.

• Example: HCl and H2O

• We can show this with arrows to represent the direction or flow of electrons. This small positive and negative charge is labeled as δ (delta). It is not a full +1 or –1 charge.

• A molecule that has two poles is called a dipolar molecule, or dipole.

There are several kinds of attractions between molecules:

1. Van der Waal forces- the attractive or repulsive force between moleculesm

– Two Types:• Dipole-Dipole Interaction• London Dispersion Forces

Dipole-Dipole interaction - The electrostatic attractions that occur between the oppositely charged regions of a dipole.

London Disperson Forces

• Dispersion- caused by the motion of the electrons, the more electrons the more force.

• A molecule with more electrons has a stronger attraction force

• Weakest type of intermolecular attraction

Hydrogen Bond

• Strongest type on intermolecular attraction

When hydrogen bonds to a very electronegative element, it has a strong dipole, therefore allowing for a fairly strong bond between the hydrogen (δ+) and the other element (δ-).

Hydrogen Bond