A chemical bond is a force that joins the atoms together. There are many different types of chemical bonds. Two main types of chemical bonds are sigma and Pi Bonds. The main difference between Pi and Sigma Bonds is due to their overlapping of atomic orbitals. The bond formed by the head-on overlapping of atomic orbitals is known as the Sigma Bond, while the bond while a Pi Bond is formed by the lateral overlapping of half-filled atomic orbitals.
Let’s take a closer look at Pi Bond vs. Sigma Bond
| Strength | Sigma Bond is stronger than the Pi Bond |
| Symbol | The symbol of Sigma Bond is σ, and the Pi Bond is π |
| Existence | Sigma Bond can exist independently, while Pi Bond always exist with sigma |
| Presence | Sigma Bond is present in alkanes, and alkenes while Pi Bond in alkenes |
Table of Contents
What is a Sigma Bond?
Sigma Bond is the strongest bond and can be found in alkanes, alkenes, and alkynes. If we look at the Sigma Bond definition, this is the bond that is formed by face-to-face overlapping of the atomic orbitals. Sigma Bonds can rotate freely and independently with less emission of energy, which makes them more stable. Due to this stability of the Sigma Bond, the bond length, bond energy, and other factors become easier to predict.
What is a Pi Bond?
A Pi Bond is weaker than the Sigma Bond and is found in the alkenes and alkynes. If we look at the Pi Bonds definition, it is the bond formed by side by side overlapping of the atomic orbitals. This bond emits a high amount of energy which makes this bond unstable. Due to the weakness of this bond, it can not react as fast as the other compounds. Another feature of the Pi Bond is that it always keeps wandering behind the Sigma Bond.
6 Key Differences Between Pi and Sigma Bond
| Components | Pi Bond | Sigma Bond |
|---|---|---|
| Formation | This bond is formed by the two Sigma Bonds | Sigma Bond formation takes place by overlapping atoms |
| Reaction | A Pi Bond is not as much reactive as a Sigma Bond | Sigma Bond is highly reactive |
| Overlapping | Pi Bond has side by side overlapping of atomic orbitals | Sigma Bond has a face to face overlapping of atomic orbitals |
| Independence | A Pi Bond is not free and independent. It always wanders around the Sigma Bond | Sigma Bond is a free and independent bond |
| Symmetry | Pi Bond does not have any symmetry | It has a cylindrical symmetry around the axis of the bond |
| Molecule Shape | This bond does not determine the shape of the molecule | The shape of the molecule is determined by this bond |
Pi vs. Sigma Bonds Similarities
- Both Pi and Sigma Bonds are formed by the overlapping of the orbitals
- Both are covalent bonds and involves in bond pairing
Pi vs. Sigma Bond Examples
Examples of Pi Bond:
- Ethylene molecule: this molecule contains one Pi Bond with five Sigma Bonds.
- Ethene: it is the simplest alkene with one Pi Bond and three Sigma Bonds
Examples of Sigma Bond:
- The bond between two hydrogen atoms is the Sigma Bond.
- A Sigma Bond is also present between the sp3 orbitals of carbon and s orbital of hydrogen in methane.
Pi vs. Sigma Bond Pros and Cons
Pros and Cons of the Pi Bond
Pros of the Pi Bond
- A Pi Bond is used to predict the behavior of the molecule in MO theory.
- It is an important covalent bond that takes part in the formation of the molecule by bonding the atoms together.
Cons of the Pi Bond
- A Pi Bond is a weak bond and not independent, as it always wanders around the Sigma Bond.
- A Pi Bond is not a stable bond, so it becomes difficult to predict bond energy and other factors.
Pros and Cons of a Sigma Bond
Pros of a Sigma Bond
- Sigma Bond is the strongest bond with high reactivity as compared to the Pi Bond.
- Sigma Bond is a free and independent bond and can remain stable on its own.
Cons of a Sigma Bond
- If we compare the Sigma Bond Vs. Pi Bond reactivity the Sigma Bond is less reactive.
- Sigma Bonds can only be formed by face-to-face overlapping of atomic orbitals.
Comparison Chart
Comparison Video
Pi vs. Sigma Bond FAQs
How Are Sigma and Pi Bonds Formed?
A Sigma Bond is formed by the face-to-face overlapping of atomic orbitals, while a Pi Bond is formed by the side-by-side overlapping.
Is a Pi Bond a Double Bond?
Pi Bonds may form a double and triple bond but do not form a single bond in most cases.
Which Bond Is Stronger, Sigma or Pi Bond?
A Sigma Bond is stronger than a Pi Bond because it has higher stability.
How Many Sigma Bonds Are in a Pi Bond?
It depends upon the type of bonds like a single bond has one Sigma Bond, the double bond has one sigma and one Pi Bond, and the triple bond has one sigma and two Pi Bonds.
How Do You Count Pi Bonds and Sigma Bonds?
These bonds can be easily calculated as Single bond= one Sigma Bond, double bond=one sigma and one pi, Triple bond= one sigma, and two Pi Bonds.
Can You Have a Pi Bond Without a Sigma Bond?
Pi Bonds can not exist independently, as they only exist in the presence of the Sigma Bond.
Conclusion
Both the sigma and Pi Bonds are types of the covalent bond and very essential in determining the shape of the molecules—the main difference in sigma vs. Pi Bonds are in their overlapping of atomic orbitals as Sigma Bond has a face to face overlapping while Pi Bond had side to side overlapping. Sigma Bond is free and dependent on high stability, while the Pi Bond is not free and has less stability. And if we talk about the reactivity in Pi Bonds vs. Sigma Bonds the Pi Bonds are more reactive because electrons are not tightly held by the nuclei.
