Polar Molecules

What is polarity?

In chemistry polarity refers to a separation of electric charge leading to a molecule or its chemical groups having an electric dipole or multipole moment. Polar molecules interact through dipole–dipole intermolecular forces and hydrogen bonds. Molecular polarity is dependent on the difference in electronegativity between atoms in a compound and the asymmetry of the compound's structure.

*Things to remember

• Polar molecules have an average charge seperation
• Unsymmetrical molecules are usually polar
• Molecular dipoles are the result of un = sharing of electrons in a molecule

Predicting Polarity

• If a molecule is symmetrical, the pull of e- is usually balanced 
• Molecules can be un-symmetrical in 2 ways

-- Diff atoms

-- Diff # of atoms

A molecule can possess polar bonds and still be nonpolar. If the polar bonds are evenly (or symmetrically) distributed, the bond dipoles cancel and do not create a molecular dipole. 

Here's a video that will explain things a bit more clearly....

Bonds

There are 3 main types of bonds in chemistry

1. Ionic (metal to non-metal)
Electrons are transferred from metal to non-metal

2. Covalent (non-metal to non-metal)
Electrons are shared between non-metals

3. Last but not least, Metallic (metal)
Holds pure metals together by electrostatic attraction

Electronegativity (en) is a measure of an atom's attraction for electrons in a bond

Atoms with greater electronegativity attract electrons

Polar Covalent bonds form from an unequal sharing of electrons, a polar covalent bond is a bond between two non-metals with different electronegativities. Unsymmetrical molecules are usually polar.
Non-Polar covalent bonds form from equal sharing of electrons, and are symmetrical molecules.
The type of bond formed can be predicted by looking at the difference in electronegativity (en) of the elements



Here are some examples!


Predict the type of bond formed.


1. H- O

2.20 - 3.44 = 1.24
This bond between Hydrogen and Oxygen is a Polar Covalent bond!


2. K-F


3.99 - 0.82 = 3.17
This bond between potassium and fluorine is an Ionic bond!

Now that we went through some examples together, let's see if you can do some on your own!

QUIZ TIME!!!! (: