Get a free home demo of LearnNext

Available for CBSE, ICSE and State Board syllabus.
Call our LearnNext Expert on 1800 419 1234 (tollfree)
OR submit details below for a call back


Valence Bond Theory

Have a doubt? Clear it now.
live_help Have a doubt, Ask our Expert Ask Now
format_list_bulleted Take this Lesson Test Start Test

Valence Bond Theory - Lesson Summary

Valence bond theory was proposed by Heitler and London in 1927 based on atomic orbitals and their configuration.

According to valence bond theory:
A covalent bond is formed when pure, valence atomic orbital of one atom overlaps with another pure, valence atomic orbital of another atom. During covalent bond formation energy releases that means stability increases.

Each of the overlapping orbitals contains the unpaired electron of opposite spin.

The electron pair is shared by both the atoms. The strongest bond is formed when the orbitals of the two atoms overlap to the maximum extent.

Based on the overlapping of orbitals, two types of covalent bonds are formed. These are known as sigma and pi bonds.

Sigma bonds are formed by the end-to-end overlap of atomic orbitals along the inter-nuclear axis known as a head-on or axial overlap.

End on over lapping is of three types, they are s-s overlapping, s-p overlapping and p-p overlapping.

A pi bond is formed when atomic orbitals overlap in such a way that their axes remain parallel to each other and perpendicular to the inter-nuclear axis.

Sigma bonds are stronger than pi bonds.

And pi bond cannot exist independently, it is formed after the formation of sigma bond.

Ex: In Ethene molecule one pi bond is formed after the formation of sigma bond.

Valence bond theory fails to determine the actual shapes of the polyatomic molecules, such as methane, ammonia and water which are Tetrahedral, Pyramidal and Bent respectively.


Feel the LearnNext Experience on App

Download app, watch sample animated video lessons and get a free trial.

Desktop Download Now
Try LearnNext at home

Get a free home demo. Book an appointment now!