Pi Bond and Sigma Bond

A chemical bond can be termed as an attraction, connection, or adhesion between two or more surfaces of molecules. It is commonly formed by links between atoms in different structures like molecules, crystals or ions. The interactions formed between the components of the atoms like protons, neutrons and electrons result in different types of chemical bonds. A chemical bond is classified into four types, they are Covalent bonds, Hydrogen bonds, ionic bonds and polar bonds. 

Covalent Bonds

Covalent bonds are known for their strong attraction forces. They are stronger bonds formed between electron pairs of atoms. The basic principle of bond formation is the stable attractive and repulsive forces between atoms. They are commonly formed between all states of matter like solid, liquid and gas. These are directional bonds that are highly powerful. Molecules that are linked by covalent bonds consist of both organic and inorganic elements. The covalent bonds can be categorised into two types based on their frequent occurrence, they are:

• π-bonds (Pi bonds)

• σ-bonds (Sigma bonds) 

Pi Bonds

Definition 

Pi bonds (π-bonds) belong to the category of Chemical covalent bonds. The letter π denoted as the title of this bond is a Greek letter. In this case, π denotes the p orbital which is an atomic orbital. Pi bonds occur as a double or a triple bond but do not exist in the form of a single bond. Pi bonds do not occur in cylindrically symmetrical form. Above and below the axis of the bonds are present the electron density. These are formed with hybrid orbitals. 

• Characteristics

A sigma bond can be categorised based on the following properties:

• These are weak bonds

• They possess oy less energy

• Pi bonds are formed between the unhybridized orbitals

• Both upper and lower nuclei consist of electron clouds 

• They are highly dependent types of bonds

• It exists as double or triple bond

• The sigma bond is formed between p-p orbitals

Examples: Some of the examples of Pi bonds are dicarbon, ethylene, diiron hexacarbonyl, and diborane.

Sigma Bonds

• Definition 

Sigma bonds (σ-bonds) is the strongest form of chemical covalent bond. The formation of this bond is facilitated by head-on overlapping between atomic orbitals. Sigma bonds form only a single bond and do not possess bonds more than that. The orbitals that facilitate sigma bonds are cylindrically symmetrical. Electron density can be detected at the central axis of the bond. These are formed by non-hybrid orbitals. The formation of a bond is facilitated by three types of overlapping. They are

• s-s orbital overlapping

• s-p orbital overlapping

• p-p orbital overlapping

• Characteristics

A sigma bond can be categorised based on the following properties:

• Sigma bonds are powerful bonds formed compared to pi bonds

• These are independent bonds

• Bonded nuclei to form the electron cloud

• Sigma bond is facilitated by both hybridized and unhybridized orbitals

• They exist as single bonds

• They play a vital role in determining the shape of a molecule

• Sigma bond formation is associated with s-s, s-p and p-p orbitals

Examples: Some of the examples of Sigma bonds are water, methane, etc.

Pi bond and Sigma Bond: Difference

The below table gives a detailed description of the differences between Pi bond and Sigma bond

Conclusion

Sigma and Pi bonds are the commonly found chemical bonds that fall under the category of covalent bonds. They play a vital role in contributing to a molecule’s shape and dimension. The products formed as the result of Covalent bonds – Sigma and Pi bonds are used for various purposes in different fields. These bonds provide us with the air we breathe, the water we drink, basic dietary compounds sugar, the fuel we use for cooking, precious stones like diamonds, daily use plastics, fuel for our vehicles, and is also involved in the production of various other commercials, industrial and domestically used products.