Sigma Bond vs Pi Bond: Difference and Comparison

In the subject of chemistry, one needs to study and have an inner for knowing how chemical bonds work. The literal definition of a bond is that it is one that keeps the binding of the atoms with each other by interacting with them.

A chemical bond is further distinguished into many times, such as the covalent bond and the polar bond. Two main chemical bonds are the Sigma bond and the Pi bond.

Key Takeaways

  1. Sigma bonds are formed by the head-on overlap of two atomic orbitals, while pi bonds are formed by the lateral overlap of two atomic orbitals.
  2. Sigma bonds are stronger than pi bonds and are responsible for the stability of molecules, while pi bonds are weaker and contribute less to the overall stability.
  3. Sigma bonds are always present in a molecule, while pi bonds may or may not be present depending on the type of bond between the atoms.

Sigma Bond vs Pi Bond

When two atoms overlap, a bond is formed between them, called a sigma bond. It is a reactive bond. The amount of energy emitted by sigma bonds is less. They are independent. A pi bond is a bond between two atoms in which their electrons from the axis join with the nuclei. They are not independent.

Sigma Bond vs Pi Bond

The formation of a sigma bond takes place in such a way that it overlaps two bonds in orbit. This happens when both the atoms appear to be face to face.

This overlapping may appear between two s and p orbitals or even in-between ones and p orbitals in an axis. The sigma bonds can roam freely and independently rotate.

The formation of a pi bond occurs in a manner formed by overlapping between two orbits in parallel or sideways. A high amount of energy emitted from this bond makes it less stable.

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When it comes to participating in a Resonance without having to show its hyper-conjuration, that is when a pi bond comes into the picture.

Comparison Table

Parameters of ComparisonSigma BondPi Bond
StrenghthThis is a strong bond.This is a weak bond
FormationFormed through the overlapping of atoms.This formed between two sigma bonds.
ReactionThis bond is highly reactive.This bond isn’t that reactive as a sigma bond.
IndependenceThese bonds are free and independent.These bonds are not free and independent.
OverlappingOverlapping of an atom in this bond can occur between one hybrid and one pure orbit or between both pure or both hybrid orbitals.Overlapping of atoms in this bond takes place only between two non-hybrid orbitals.
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What is Sigma Bond?

The formation of a sigma bond takes place in such a way that it overlaps two bonds in orbit. This happens when both the atoms appear to be face to face.

This overlapping may appear between two s and p orbitals or even in-between ones and p orbitals in an axis. The sigma bonds can roam freely and independently rotate.

A sigma bond is very less in emitting energy, which makes it more stable. A sigma Bond does not show any Resonance or hyper-conjugation.

A pair of electrons exists between every two atoms that can move to another atom. This helps them to be a Delocalized bond.

A single Lewis structure in compounding can fully elaborate a compound with a localised sigma. The sigma bonds can roam freely and independently rotate.

It is very easy to predict a bond’s length, a bond’s energy, and other factors when it comes to sigma bonds.

What is Pi Bond?

The formation of a pi bond occurs in a manner formed by overlapping between two orbits in parallel or sideways. A high amount of energy emitted from this bond makes it less stable.

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When it comes to participating in a Resonance without having to show its hyper-conjuration, that is when a pi bond comes into the picture.

In this kind of bond, there can be more than one pair of electrons between an atom which can move from one atom to another. This helps to make a Delocalized bond.

Features like knowing how to bond systems can be figured by all the single, double and triple bonds.

These bonds are very weak as they are bonded very loosely. The Pi bonds do not react that fast as compared to other bonds because of their characteristics of being weak bonds.

This means no kind of symmetry exists between the Pi bonds. One important feature of a pi bond is that they always keep roaming behind the sigma bonds.

Main Differences Between Sigma Bond and Pi Bond

  1. A Sigma bond is a strong bond compared to a Pi bond, and on the other hand, a Pi bond is weaker than a Sigma bond.
  2. When an atom interacts, this is when a sigma bond is formed. And on the other hand, a pi bond forms when two atoms of sigma bonds are formed between them.
  3. When there is a bonding between two atoms, there can be only one sigma formed that is formed, and on the other hand, when there is a bonding between two atoms, there can be the existence of two pi bonds.
  4. A sigma bond in an atom is proved scientifically to be highly reactive by nature, and on the other hand, a Pi bond in an atom is said to be less reactive as compared to sigma bonds.
  5. Sigma bonds are bonds that exist independently and roam freely in orbit, and on the Other hand, pi bonds cannot roam freely and independently as they have a restricted rotation.
References
  1. https://www.sciencedirect.com/science/article/pii/000926149285453H

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About Author

Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.