The Difference Between Sigma Bond and Pi Bond Explained
Chemistry is a vast area of science, and there are many concepts that we need to understand. One of these concepts is the difference between sigma bond and pi bond. In this article, we will discuss the two bonds, what they are, their differences, and their functions in chemical bonding.
What is a Sigma Bond?
A sigma bond, represented as σ, is the strongest type of covalent chemical bond formed between atoms of different elements. Sigma bonds result from the overlapping of two atomic orbitals along the internuclear axis. This overlapping results in the formation of a region of electron density that is concentrated along the internuclear axis between the two bonding atoms, giving rise to the name “sigma.”
Sigma bonds are formed between two atoms in a direct head-on collision, and are therefore responsible for the single bond formation. Some common examples of single sigma bond formation are found in molecules such as H2, HBr, HCl, and CH4.
What is a Pi Bond?
A pi bond, represented as π, is a type of chemical bond formed by the overlapping of two atomic orbitals that are not collinear. The pi bond is formed when two p orbitals that are parallel to each other overlap, with the electron density being located above^ or below_ the internuclear axis. Unlike a sigma bond, a pi bond does not result from a direct head-on collision.
Pi bonds are responsible for double and triple bond formation. In molecules like C2H4, ethene, the double bond between two carbon atoms is composed of one sigma bond and one pi bond. The triple bond between two nitrogen atoms in the N2 molecule is composed of one sigma bond and two pi bonds.
What are the Differences Between Sigma Bond and Pi Bond?
There are several differences between sigma bonds and pi bonds. These differences are as follows:
1. Formation: Sigma bonds are formed by a direct head-on collision, whereas pi bonds are formed when two parallel orbitals overlap.
2. Location: Sigma bonds are located along the internuclear axis, whereas pi bonds exist above^ or below_ the internuclear axis.
3. Strength: Sigma bonds are stronger than pi bonds.
4. Bond orders: Sigma bonds are responsible for the single bond formation, while pi bonds are responsible for double and triple bonds.
Conclusion
Sigma bond and pi bond are two essential concepts in chemistry. They play a crucial role in chemical bonding, and their formation leads to the formation of different types of compounds. Understanding these bonds can help in understanding various chemical reactions and their mechanisms. Remember, sigma bonds are head-on, stronger, and responsible for single bond formation, while pi bonds are parallel and responsible for double and triple bond formation.
Table difference between sigma bond and pi bond
| Sigma bond | Pi bond |
|---|---|
| Sigma bond is formed by the head-on overlap of atomic orbitals along the internuclear axis. | Pi bond is formed by the lateral overlap of atomic orbitals above and below the internuclear axis. |
| Sigma bond is a stronger bond than a pi bond. | Pi bond is weaker than a sigma bond. |
| Sigma bond allows free rotation around its axis. | Pi bond restricts free rotation around its axis. |
| Sigma bond is formed by the hybrid orbitals such as sp, sp2, and sp3. | Pi bond is formed by the unhybridized p orbitals. |
| Sigma bond is symmetric with respect to the internuclear axis. | Pi bond is asymmetric with respect to the internuclear axis. |