Difference Between Sigma and Pi bond 

The main differences between sigma and pi bonds lie in their formation and strength:

1. Formation:
   • Sigma Bonds: These bonds form through direct head-to-head overlap of atomic orbitals along the internuclear axis, which is known as axial or end-to-end overlap. This type of overlap involves s orbitals, p orbitals, or hybrid orbitals.
   • Pi Bonds: These bonds form through side-to-side overlap of parallel p orbitals. This overlap occurs above and below the plane of the nuclei of the bonding atoms.
2. Strength:
   • Sigma Bonds: Sigma bonds are stronger than pi bonds because the head-to-head overlap allows for greater orbital interaction, resulting in a stronger bond.
   • Pi Bonds: The side-to-side overlap in pi bonds is less effective, leading to a weaker bond compared to sigma bonds.
3. Bond Characteristics:
   • Sigma Bonds: They can exist independently as single bonds and do not require the presence of pi bonds.
   • Pi Bonds: Pi bonds cannot exist without an underlying sigma bond. They typically accompany sigma bonds in double and triple bonds.

Sigma bonds’ strength and primary formation make them fundamental in single bonds, while pi bonds add to the bond order and contribute to the properties of double and triple bonds.

What is a Sigma Bond?

A sigma bond (σ bond) is the strongest type of covalent bond, formed by the head-on overlap of atomic orbitals. Sigma bonds are found in alkanes, alkenes, and alkynes. Below is an example of how a sigma bond forms between orbitals:

Properties of Sigma Bonds:

1. Formation: Created by the linear overlap of s-s, s-p, or p-p orbitals.
2. Symmetry: Cylindrically symmetrical around the bond axis.
3. Strength: Significantly stronger due to maximal overlap.
4. Molecular Orbitals: Comprised of sigma molecular orbitals.

What is a Pi Bond?

A pi bond (π bond) is a type of covalent bond formed by the lateral overlapping of half-filled atomic orbitals. Pi bonds are typically found in alkenes and alkynes. Below is an example of how a pi bond forms between two orbitals:

Properties of Pi Bonds:

1. Formation: Generated by the side-by-side overlap of atomic orbitals.
2. Electron Cloud: Features two sections of the electronic cloud above and below the two nuclei.
3. Strength: Weaker than sigma bonds due to less overlap.
4. Molecular Orbitals: Consists of pi molecular orbitals.

Why is a Sigma Bond Stronger than a Pi Bond?

Sigma bonds are stronger than pi bonds because they involve head-on overlapping of orbitals, resulting in greater overlap and stronger interaction. In contrast, pi bonds involve parallel orbital paths with less overlap between p-orbitals, leading to a weaker bond.

Differences Between Sigma and Pi Bonds

1. Overlap Type: Sigma bonds result from head-on overlap, while pi bonds result from lateral overlap.
2. Strength: Sigma bonds are stronger due to greater overlap.
3. Symmetry: Sigma bonds are cylindrically symmetrical; pi bonds have electron clouds above and below the bond axis.
4. Occurrence: Single bonds are always sigma bonds; in double and triple bonds, one is sigma, and the others are pi bonds.

Key Points:

• Single bonds are sigma bonds.
• In double bonds, one is sigma and one is pi.
• In triple bonds, one is sigma and two are pi.
• Sigma bonds involve s-s, s-p, or p-p overlap.
• Pi bonds form from parallel p orbitals’ sideways overlap.