Difference Between Sigma Bond And Pi Bond

The major difference between sigma bond and pi bond is that Sigma bonds (σ) are single covalent bonds formed by the direct overlap of atomic orbitals along the bond axis, allowing free rotation while Pi bonds (π) are double or triple covalent bonds formed by the side-to-side overlap of p orbitals, restricting rotation and creating a weaker bond.

What Is Sigma Bond?

A sigma (σ) bond is a type of covalent chemical bond formed between two atoms when their atomic orbitals overlap head-on along the bond axis. Sigma bonds are typically found in single bonds (sigma single bonds) and represent the strongest and most stable type of covalent bond.

They allow for free rotation around the bond axis, making them flexible and less restricted in terms of molecular structure.

Example of Sigma Bond

In a Lewis structure or molecular orbital diagram, the sigma bond in H2 is typically depicted as H-H or σ(H-H).

What Is Pi Bond?

A pi bond (π bond) is a type of covalent bond formed when two atomic orbitals overlap side by side in a double or triple bond. Unlike sigma bonds, which have direct head-on overlap, pi bonds involve the parallel overlap of two p orbitals (or d orbitals in triple bonds) above and below the bond axis.

Pi bonds are weaker than sigma bonds and restrict the rotation of atoms around the bond axis, contributing to the rigidity of double and triple bonds in molecules.

Example of Pi Bond

An example of a pi (π) bond can be found in the ethene (ethylene) molecule, which is composed of two carbon atoms double-bonded to each other and each bonded to two hydrogen atoms. The pi bond exists in the double bond between the two carbon atoms.

Sigma Bond Vs Pi Bond

The primary difference between the sigma bond and the pi bond is given below:

CharacteristicSigma (σ) BondPi (π) Bond
Type of OverlapHead-on overlapSide-to-side overlap
Bond LocationAlong the bond axis (internuclear axis)Above and below the bond axis
Number of BondsEvery single bond has one sigma bondTypically found in double and triple
StrengthGenerally strongerGenerally weaker
Bonding ElectronsOccupy a cylindrical space between atoms along the bond axisOccupy two parallel regions above and below the bond axis
MobilitySigma bonds allow the rotation of atomsSigma bonds allow the rotation of atoms

Leave a Comment