Polarity and Bonding
v Electronegativity
Ø This is a value that describes the electron density of a given atom.
Ø Electronegativity trends up and to the right on the periodic table with Fluorine at
the highest (4.0) and Francium at the lowest (0.7)
Ø The difference in electronegativity between two atoms is calculated as such:
∆𝐸𝑁 = 𝐸𝑁!"#$%&' &$)* − 𝐸𝑁&$$&!+", &$)*
v Bond Polarity
Ø The type of bond between two atoms can be determine based on the bonds’ ∆𝐸𝑁
§ > 1.7 is an ionic bond. The electrons are not equally shared and charges exist
on each atom.
§ 0.4 – 1.7 is a covalent bond. The electrons are shared in an electron orbital
spread out between the bonding atoms.
§ < 0.4 is a very nonpolar covalent bond.
v Molecular Polarity
Ø Determining molecular polarity requires you to evaluate two things:
§ 1.) What is the ∆𝐸𝑁 of the bonds present in the molecule?
§ 2.) What is the resulting VESPER shape of the molecule?
Ø If ∆𝐸𝑁 is high and the shape of the molecule is asymmetrical, there is polarity
across the molecule.
Ø If ∆𝐸𝑁 is low and the shape of the molecule is symmetrical, there is no polarity
across the molecule.