The Difference between Sigma and Pi Bond
When it comes to understanding chemical bonding, two of the most important terms that you need to know are sigma bonds and pi bonds. These two types of bonds are essential in defining some of the physical and chemical properties of molecules. Here’s a closer look at the difference between sigma and pi bonds.
What is a Sigma Bond?
A sigma bond is a type of covalent bond in which the electron density is concentrated along the imaginary line that connects the two atomic nuclei. This line is known as the internuclear axis, and the bond is designated with the Greek letter σ. Sigma bonds form when overlapping atomic orbitals share electron pairs between atoms. In simpler terms, sigma bonds are formed when two atoms come close to each other and their electron clouds overlap head-to-head directly.
Sigma bonds are the strongest type of covalent bonds and are responsible for the stability of the molecule’s structure. They are found in single bonds as well as multiple bonds between the same or different atoms.
What is a Pi Bond?
A pi bond is a type of covalent bond in which the electron density is concentrated above and below the plane formed by the two atomic nuclei. These bonds are designated by the Greek letter π. Pi bonds form when overlapping atomic orbitals share electron pairs between atoms, but this sharing occurs in a sideways or lateral manner. In other words, the electrons in pi bonds are not overlapping directly, but they are interacting in a perpendicular orientation.
Pi bonds are weaker than sigma bonds and depend on the existence of sigma bonds to form. They are found only in multiple bonds and fill the space between two atoms. Pi bonds are responsible for many of the unique chemical and physical properties of molecules such as double and triple bonds, conjugation, and aromaticity.
The Key Differences between Sigma and Pi Bonds
Sigma and Pi bonds are different from each other and have unique characteristics that define them. The key differences between sigma and pi bonds are:
– Sigma bonds form head-to-head, while pi bonds form in a sideways or lateral manner.
– The electron density in sigma bonds is concentrated along the internuclear axis, while the electron density in pi bonds is concentrated above and below this axis.
– Sigma bonds are stronger than pi bonds.
– Sigma bonds occur in both single and multiple bonds, while pi bonds are found only in multiple bonds.
In conclusion, sigma and pi bonds play important roles in covalent bonding and define many of the properties of molecules. Understanding the difference between these two types of bonding can help you understand the physical and chemical properties of molecules better.
Table difference between sigma and pi bond
| Characteristics | Sigma Bond | Pi Bond |
|---|---|---|
| Definition | The covalent bond formed by the overlap of orbitals along the axis connecting two atomic nuclei. | The covalent bond formed by the sideways overlap of two atomic orbitals. |
| Shape | Straight and linear | Planar and perpendicular |
| Strength | Stronger | Weaker |
| Types | Single, double or triple bonds | Double or triple bonds |
| Occurrence | Occurs in all covalent compounds | Only in compounds with multiple bonds |