Sigma vs. Pi Bond — What's the Difference?
Edited by Tayyaba Rehman — By Fiza Rafique — Published on December 31, 2023
Sigma bonds are single covalent bonds formed by the head-on overlapping of atomic orbitals, while Pi bonds are formed by the side-to-side overlapping of p-orbitals.
Difference Between Sigma and Pi Bond
Table of Contents
ADVERTISEMENT
Key Differences
Sigma bonds are the most basic type of bond, formed by the direct overlap of atomic orbitals, creating a strong and linear connection between the bonding atoms. On the other hand, Pi bonds emerge from the side-to-side overlap of p-orbitals and exist over and above sigma bonds in double or triple bonds.
Sigma bonds allow free rotation of bonded atoms because of their axial overlapping, ensuring a solid connection. In contrast, Pi bonds restrict this rotation due to their lateral overlapping, introducing rigidity in the molecular structure.
When visualizing the electron cloud, the sigma bond appears symmetrical along the bond axis, whereas the electron density in a Pi bond is found above and below the bonding axis.
Both Sigma and Pi bonds play a vital role in determining the structure and reactivity of molecules, with Sigma bonds being more prevalent, and Pi bonds conferring specific characteristics to double and triple bonded compounds.
Comparison Chart
Formation
Direct overlap of atomic orbitals
Side-to-side overlap of p-orbitals
ADVERTISEMENT
Bonding Orbitals
S, p, d
Primarily p
Bond Strength
Generally stronger
Weaker than Sigma bonds
Bond Rotation
Allows free rotation
Restricts rotation
Appearance in Molecules
Present in all single, double, and triple bonds
Present only in double and triple bonds after Sigma bond
Compare with Definitions
Sigma
Sigma bonds are single covalent bonds.
The carbon-carbon connection in ethane consists of a Sigma bond.
Pi Bond
Pi bonds result from the sideways overlap of orbitals.
The double bond in ethene consists of one Sigma and one Pi bond.
Sigma
Sigma bonds result from the head-on overlap of orbitals.
Direct overlap of two s-orbitals forms a Sigma bond.
Pi Bond
Pi bonds are present in double and triple covalent bonds.
Ethyne has a Sigma bond and two Pi bonds.
Sigma
Sigma bonds are prevalent in all types of covalent bonds.
Whether it's a single or a triple bond, a Sigma bond is always present.
Pi Bond
Pi bonds are generally weaker than Sigma bonds.
Breaking a Pi bond requires less energy compared to a Sigma bond.
Sigma
Sigma bonds allow for molecular rotation.
Due to the Sigma bond in ethane, its hydrogens can rotate freely.
Pi Bond
Pi bonds introduce rigidity into molecular structures.
Due to the Pi bond, the atoms in ethene can't rotate around the double bond.
Sigma
Sigma bonds generally have higher bond energies.
The bond energy of a Sigma bond often exceeds that of a Pi bond.
Pi Bond
Pi bonds have electron density above and below the bond axis.
The electron cloud of a Pi bond is distinctively distributed around the bonding atoms.
Sigma
The 18th letter of the Greek alphabet. See Table at alphabet.
Sigma
A sigma factor.
Sigma
(Statistics) The standard deviation of a given probability distribution or a given set of data.
Sigma
The eighteenth letter of the Classical and Modern Greek alphabets, the twentieth letter of Old and Ancient.
Sigma
(mathematics) The symbol Σ, used to indicate summation of a set or series.
Sigma
(statistics) The symbol σ, used to indicate one standard deviation from the mean, particularly in a normal distribution.
Sigma
Clipping of sigma male
Sigma
The Greek letter
Sigma
The 18th letter of the Greek alphabet
Common Curiosities
Can molecules with Pi bonds rotate freely?
No, Pi bonds restrict the free rotation of bonded atoms.
Can a molecule have both Sigma and Pi bonds?
Yes, molecules with double or triple bonds have both Sigma and Pi bonds.
Which bond restricts rotation, Sigma or Pi bond?
Pi bonds restrict rotation due to their lateral overlapping.
Which bond is generally stronger, Sigma or Pi bond?
Sigma bonds are generally stronger than Pi bonds.
What orbitals primarily contribute to Pi bonds?
Pi bonds primarily arise from the side-to-side overlap of p-orbitals.
Can d-orbitals participate in Sigma bonding?
Yes, d-orbitals can also participate in Sigma bond formation.
Why are molecules with Pi bonds often more reactive?
Pi bonds are generally weaker and more exposed, making them more susceptible to reactions.
Are Sigma bonds present in every covalent bond?
Yes, Sigma bonds are present in all single, double, and triple covalent bonds.
In a carbon-carbon triple bond, how many Sigma and Pi bonds are present?
In a carbon-carbon triple bond, there is one Sigma bond and two Pi bonds.
What is a Sigma bond?
A Sigma bond is a single covalent bond formed by the direct overlap of atomic orbitals.
How is a Pi bond different from a Sigma bond?
A Pi bond results from the side-to-side overlap of p-orbitals and is found in addition to a Sigma bond in double and triple bonds.
How many Sigma and Pi bonds are in a double bond?
A double bond has one Sigma bond and one Pi bond.
Are Sigma bonds involved in hybridization?
Yes, Sigma bonds often involve hybridized atomic orbitals.
Is the electron cloud of a Pi bond symmetrical?
No, the electron density of a Pi bond is distributed above and below the bond axis.
Can single bonds have Pi bonds?
No, single bonds consist of only Sigma bonds.
Share Your Discovery
Previous Comparison
Managing Director vs. Whole time Director
Next Comparison
FHD vs. LEDAuthor Spotlight
Written by
Fiza RafiqueFiza Rafique is a skilled content writer at AskDifference.com, where she meticulously refines and enhances written pieces. Drawing from her vast editorial expertise, Fiza ensures clarity, accuracy, and precision in every article. Passionate about language, she continually seeks to elevate the quality of content for readers worldwide.
Edited by
Tayyaba RehmanTayyaba Rehman is a distinguished writer, currently serving as a primary contributor to askdifference.com. As a researcher in semantics and etymology, Tayyaba's passion for the complexity of languages and their distinctions has found a perfect home on the platform. Tayyaba delves into the intricacies of language, distinguishing between commonly confused words and phrases, thereby providing clarity for readers worldwide.
