Sigma and pi bond overview
Basically in covalent bonding, we generally say that it is the nuclear pull between two bonding atoms. If we look deep into covalent bonding we will find that bonding is the overlapping of orbitals of atoms that undergoes bonding. The overall process of covalent bonding is basically when nuclear pull attracts atoms toward each other they come closer to each other. When the atomic orbitals cross each other and cause bonding. This atomic orbitals crossing is actually of two types, one is named as sigma overlapping and the second is pi overlapping. When atomic orbitals cross each other face to face then bond formation due to this type of overlapping is called Sigma bond. When atomic orbitals cross each other sideways then bond formation due to this type of overlapping is called pi bond. Single bond has face to face bonding or in simple words single bond is sigma bond. Double bond contain one sigma and one pi bond. Triple bond is one sigma and two pi bond. So here is detailed description about Sigma and pi bond.
What is Sigma bond ?
Bonds of this type are covalent in nature. Sigma bonds are the product of head on approach of one atomic orbital to other. Sigma bond is very strong bond due to high extent of overlapping between bonding orbitals. Here are few examples of sigma bonds.
Examples : Molecule of Hydrogen H2 is formed as a result of sigma bond between two Hydrogen atoms. Same molecule of HF is result of sigma bond between Hydrogen and Folurine atom.
Characteristics of Sigma bonds :
- Sigma bonds are stronger bond.
- Sigma bonds are bonds with high energy.
- Electronic cloud is present between the bonded nuclei.
- Both hybridize and unhybirdize orbital form sigma bond.
- Sigma bond can exist independently.
- Single bond is always a sigma bond.
- Essential role in determining the shape of molecule.
- s-s, s-p and p-p orbitals form sigma bond.
Ways of formation of Sigma bond :
Sigma bond formation is of three types. This division is on the basis of type of atomic orbitals overlap with each other. So these three types are given below,
- S-S overlapping
- S-P overlapping
- P-P overlapping
Sigma bond due to s-s overlapping :
In this type of covalent bonding sigma bond formation is due to the overlapping of two bonding s orbitals. In such type of bond formation it is necessary that both bonding orbitals should be half filled. Example of such type of sigma bonded molecule is H2.
Sigma bond due to s-p overlapping :
In this type of covalent bonding sigma bond formation is due to the overlapping of two bonding orbitals one is s and the second is p orbital. In such a type of bond formation, it is necessary that both bonding orbitals s and p should be half-filled. An example of such type of sigma bonded molecule is HF.
Sigma bond due to p-p overlapping :
In this type of covalent bonding sigma bond formation is due to the overlapping of two bonding p orbital. In such a type of bond formation, it is necessary that both bonding p orbitals should be half-filled. An example of such a type of sigma bonded molecule is F2.
What is a pi bond?
These bonds are also covalent in nature. A pi bond is a product of overlapping between orbitals by side way approach or in parallel to each other. It is represented by the π sign.
Examples of pi bond: Ethylene contains 5 sigmas and one pi bond is an example of pi bonding.
Characteristics of pi bonds :
- Pi bonds are weaker bonds.
- Pi bonds are bonds with less energy.
- Electronic cloud is present upper or lower to bonded nuclei.
- Only un hybridized orbitals form pi bonds.
- Pi bond can not exist independently.
- A double bond contains one pi bond and a triple bond contain two pi bond.
- p-p orbitals form a sigma bond.
Which one is the stronger bond sigma or pi?
The Sigma bond is stronger than the pi bond. Moreover sigma bond has more energy than a pi bond. Why sigma bond is stronger than the pi bond? The answer to this question is given below.
Why Sigma bond is stronger than the pi bond?
The strength of the covalent bond is totally on the extent of overlapping between orbitals. The more overlapping the stronger the bond is. In the case of the sigma and pi bond. Sigma bond has more overlapping of atomic orbitals as compared to the pi bond. So more overlapping more stronger the bond will be. Due to high overlapping, the sigma bond is strong and has more energy. More Is overlapping. That’s why the sigma bond is stronger than the pi bond. Sigma bond has more stability than pi bond.