Introduction to Molecular Geometry & Bonding Theories

Introduction

Polarity of the bond depends on the ability of one atom to attract the electrons of the bonds towards it more than the other atom.
polar-nonpolar

Which is based on the difference in electronegativity between the two atoms making the bond.

A polar molecule does not necessarily contain polar bonds
It is possible for a molecule to contain polar bonds, but not to be polar.

Example: CO2 molecule

co2-polar-bonds

In a CO2 molecule, C−O bond is polar, so both C−O bonds in CO2 are polar, but CO2 is not a polar molecule.

What is the reason behind this?
# e domains around C = 2; the molecule has a linear geometry.
The two dipoles are opposite to each other along the same line; they cancel each other.
co2-polar-bonds2

Example: H2O molecule

Molecular Geometry
In a H2O molecule; # e domains around O = 4; hence not linear.
Bond dipoles DO NOT cancel each other.
So, H2O is a POLAR molecule.

 h2o-polar-bonds
Hence, overall polarity of the molecule depends on its molecular geometry.

Exercises on Molecular Shape and Molecular Polarity

Exercise I: Molecular Shape and Molecular Polarity

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 Solutions

Exercise II: Molecular Shape and Molecular Polarity

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 Solutions


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