Differences to Remember between Sigma and Pi Bond

Chemical bonds are responsible for holding atoms together. Chemical bonding can occur in four ways: covalent, coordinate, ionic, and hydrogen linkages. 

The major distinguish Between Sigma and Pi Bond is that a covalent bond is a type of link that is formed when two atoms share electrons, as described by chemistry. It is referred to as a molecular bond in another context.

Knowing more about the bonds

Interactions that account for the affiliation of atoms in molecules, crystals, and other stable species that make up the recognisable substances of the daily world are known as chemical bonding. 

Chemical bonding Nuclei and electrons interact as atoms approach one another, causing the total energy to drop below what it would be in any other configuration. Atoms link together when their total energy is less than the sum of their energies. 

This energy reduction is known as bonding energy. In the early 20th century, once the electron was discovered and quantum mechanics gave a vocabulary for describing the behaviour of electrons in atoms, theories that helped define the nature of chemical bonding came to fruition. 

Chemical engineers require quantum mechanics to explain bond formation quantitatively, but their grasp of bonding is mostly stated in intuitive models that are quite straightforward. These models consider ionic and covalent bonds to be the most common types of bonding. Periodic table positions can predict what sort of bond will form between any two atoms, and features of substances generated due to that bonding may be linked to that type.

Sigma Bond

In chemistry, a sigma bond (bond) is the strongest covalent chemical link formed between two molecules. It is formed when atomic orbitals clash with one another. Understanding Sigma bonds in diatomic molecules are made easier by employing symmetry group terminology and procedures, which are described below. 

When analysing a -bond using this formal approach of bond analysis, the bond is symmetrical concerning rotation about the bond axis. According to this notion, the most prevalent sigma bonds consist of two protons and two electrons (or vice versa) (where z is defined as the axis of the bond or the internuclear axis). 

According to quantum theory, Molecular orbitals (MO) with identical symmetry can mix or hybridise. As a result of mixing diatomic molecules, the wavefunctions s+s and pz+pz molecular orbitals merge into a single wavefunction. The mixing (also known as hybridisation or blending) will vary in strength depending on the relative energies of the MOs with comparable symmetry between them.

H2 1s* antibonding molecular orbital with nodal plane in the H2 1s* molecule When it comes to homodiatomics (homonuclear diatomic compounds), there aren’t any nodal planes where the wavefunction of bonding orbitals is zero, either between the connected atoms or via the linked atoms. The analogous antibonding orbital, often known as the * orbital, is defined by one nodal plane between the two connected atoms.

There are sigma bonds that are the strongest because their orbitals immediately overlap, and the electrons that are a part of these bonds are sometimes referred to as sigma electrons. Sigma bonds are formed when the orbitals of two atoms overlap entirely.

The sign represents the Greek letter sigma, which is represented by the number one. When seen along the bond axis, a MO exhibits circular symmetry, so it is referred to as an “s” atomic orbital in some circles.

Among single bonds, the most prevalent is the sigma bond, which comprises a sigma bond plus one or more additional bonds, such as the pi bond. The sigma bond is equal to the pi bond in terms of strength when it comes to chemical bonding.

Pi Bonds (π Bonds)

As defined in chemistry, pi bonds (also known as “π bonds”) are chemical bonds in which two lobules of an orbital (on one atom) overlap with two lobules of an orbital (on another atom), and in which this overlap happens laterally between the two lobes of an orbital on the other atom. In each of these atomic orbitals, the electron density is zero, and they are all located on the same nodal plane that goes between the two tightly bound nuclei. 

This plane also serves as a nodal plane for the pi bond’s molecular orbital, which is in this plane. Double and triple bonds can form pi bonds, whereas single bonds are not capable of forming pi bonds in most circumstances.

They were given this name because the orbital symmetry of the pi bond is identical to that of the p orbital when seen from the bond axis. The Greek letter “p” appears in their name to allude to p orbitals. One typical type of pi bonding includes the p orbitals themselves. However, d orbitals can also participate in this type of bonding. This latter model serves as a foundation for metal-metal multiple bonding and is a subset of it.

Pi bonds are weaker than sigma bonds because they have a smaller diameter. The bond energy of the C-C double bond, which is composed of one sigma bond and one pi bond, is less than double that of the bond energy of the C-C single bond. It suggests that the stability supplied by the pi bond is less than the stability added by the sigma bond. 

According to quantum physics, the weakness of this bond may be explained by the fact that there is substantially less overlap between the component p-orbitals as a result of their parallel orientation. 

On the other hand, Sigma bonds generate bonding orbitals directly between the nuclei of the bonding atoms, resulting in a bigger overlap and a stronger sigma bond resulting from the direct formation of bonding orbitals.

In the presence of two areas of overlap, pi bonds are formed by the overlap of atomic orbitals in touch with one another. Pi bonds have a greater degree of diffuseness than sigma bonds. Pi electrons are electrons that are found in pi bonds and are occasionally referred to as such. Because rotation entails removing the parallel orientation of the constituent p orbitals, it is not possible for a molecule fragment linked by a pi bond to rotate around that connection without breaking the pi bond as a result.

For diatomic compounds with a single nucleii, bonding molecular orbitals have just one nodal plane going through the bound atoms and no nodal planes between the bonded atoms. In contrast, nonbonding molecular orbitals have no nodal planes between the bonded atoms. The presence of an extranodal plane between these two bound atoms defines the equivalent antibonding molecular orbital, often known as the * (“pi-star”) molecular orbital.


This post discussed covalent bonds, namely sigma and pi bonds, and nothing else. In addition, we explained what a sigma bond is and how it varies from a pi bond in terms of structure.


Go to Smartblog Theme Options -> Ad Management to enter your ad code (300x250)

No comments yet.

Leave a Comment