Sigma and Pi Bonds

Introduction to Sigma and Pi bonds

The Sigma and Pi bonds are distinguished by the overlapping of atomic orbitals. This overlapping ultimately forms the covalent bonds. The sigma bonds are formed by the head-to-head overlapping of the atomic orbitals, whereas; the pi bonds are formed by the lateral overlap of two atomic orbitals. 

Both Sigma and Pi are Greek words. Note, the sigma bond is denoted by (σ); however, the pi bond is denoted by (π). Several bond parameters, including the bond length, bond angle, and bond enthalpy, are highly dependent on how atomic orbitals overlap. Today, in this article, we will discuss the Sigma and Pi bonds in detail along with other related concepts. Without any further ado, let’s get started! 

What is a Sigma bond? 

The sigma bond is denoted by (σ), a covalent bond primarily formed by head-on positive, also known as the same phase overlap of the atomic orbital and internuclear axis. Compared to other covalent bonds, the sigma bonds are the strongest as they directly overlap the participating orbitals. The participating electrons in the sigma bond are popularly known as the σ electrons. It is mostly seen that all the single bonds are only the sigma bonds. These are formed through several combinations of the atomic orbital. 

s-s Overlapping 

In the S-S overlapping, one “s” orbital from every atom taking part goes for the head-on overlapping with the internuclear axis. Before the “s” orbital overlaps with another, it should be half-filled. When two s orbitals overlap, it leads to the sigma bond formation. This kind of overlap mostly occurs in H2

s-p Overlapping 

In the s-p overlapping, the half-filled s orbital is overlapped by the one half-filled p orbital with the internuclear axis that forms a covalent bond. This kind of overlapping mostly occurs in ammonia. 

p-p Overlapping 

In the p-p overlapping, one half-filled p orbital from all-atoms taking part undergoes head-on overlapping with the internuclear axis. This kind of overlapping mostly occurs in Cl2

. If there are two p orbitals, head-to-head overlapping gives rise to a sigma bond. However, the Pi bond is generated with the lateral overlapping of these orbitals. 

What is Pi Bond? 

Pi bonds are denoted by (π). These are formed through the sidewise positive or the same phase overlapping the atomic orbitals with the direction perpendicular to the internuclear axis. When the Pi bond forms, the atomic orbitals axes are parallel to one another; however, the overlapping is directly perpendicular along with the internuclear axis. Compared to sigma bonds, the Pi bonds are generally weaker because they hold a lower degree of overlapping. 

Mostly, a double bond holds one pi bond and one sigma bond. However, a typical triple bond leads to the formation of one σ bond and two π bonds. Note that the sigma and pi bonds combination is always better and stronger as compared to the single sigma bond.

Difference between the Sigma and Pi bonds

Here are the key differences between the Sigma and Pi bonds – 

What are Bond Parameters? 

Bond parameters can be defined as the covalent bonds characterised based on multiple bond parameters, including bond length, bond angle, bond order, and bond energy, popularly known as the Bond Enthalpy. The bond parameters play a significant role in offering insights into the chemical compound stability and chemical bonds strength that holds its atoms together.

Introduction to Bond Length

The bond length can be described as the total distance between the centres of 2 covalently bonded atoms. The bond length is generally evaluated by the bond order or the total number of bonded electrons. 

For the covalent bonds, the length of the bond is inversely proportional to the order bond. The higher the bond orders are, the stronger bonds that are further accompanied by the robust forces of attraction that hold the atoms together and close to one another. The short bonds are formed because of an extreme force of attraction. The length of the bond increases in the following order-  triple bond < double bond < single bond.

Introduction to Bond Order

The covalent bond’s bond order can be defined as the total number of covalently bonded electrons that pairs between the two atoms in the molecule. It can be easily found while making the lewis structure of the molecule and determining the electron pairs in atoms.

Introduction to Bond energy 

In simple terms, the bond energy, also known as the bond enthalpy, can be defined as the strength measure of a chemical bond. It refers to the energy needed to break all the covalent bonds of only one type in one mole of a chemical compound. It is in a gaseous state. It is critical to note that the bond dissociation energy is not similar to the bond energy. The latter part is the energy Enthalpy associated with homolytic cleavage of the bond in a molecule. 

Conclusion 

With this, we come to an end of our today’s discussion about Sigma and Pi Bonds. Today, in this article, we covered multiple areas of Sigma and Pi Bonds, including the definition of Sigma and Pi bonds, combinations of atomic orbitals, along with differences between the Sigma and Pi Bonds. We hope, This study material on Sigma and Pi bonds must have helped to attain a greater understanding of Sigma and Pi bonds along with other related topics of Sigma and Pi Bonds.