Hybridization of carbon

Hybridization of carbon is the mixing of 2s and 2p orbitals by promoting a 2s electron to a 2p suborbital of carbon, when it (carbon) is reacting with other elements.

In ground state, carbon with electronic configuration 1S²2S²2P² seems to have a covalency of two since the two atoms have only two paired electrons.

Figure 1 Carbon in ground state

However, when carbon combines with other atoms, sufficient energy is required to unpair the 2S electrons. The atom then gets unpaired electrons and shows a covalency of 4.

Figure 2 Carbon atom in excited state

Types of Hybridization in Carbon

1. sp Hybridization

The sp hybridisation involves hybridisation of one 2s-orbital and one 2p-orbital, forming two hybrid orbitals of the same energy leaving two 2p-orbitals unaffected. The hybridisation occurs in compounds with triple bonds like alkynes etc.

When the hybridization occurs, the molecules have a linear arrangement of the atoms with a bond angle of 180°.

Example: Ethyne.

2. sp2 Hybridization

In this type of  hybridization, carbon-carbon double bonds consist of one sigma bond and one pie bond to form a double bond. A pie bond is a type of a bond formed when two parallel p-orbitals of adjacent atoms overlap laterally. This involves the hybridization of one 2s orbital with two 2p orbitals, forming three sp2 hybrid orbitals of the same energy leaving one 2p-orbital unaffected. Hybrid orbitals are placed in a triangular arrangement with 120° angles between bonds.

Example: Ethenes

 

3. sp3 Hybridization

In this type of hybridization, the carbon atom is bonded to four other atoms by sigma bonds leading to the formation of sp3 hybridization. Sigma bond is a covalent bond formed by the overlap of s and p orbitals. Here 1 s orbital and 3 p orbitals in the same shell of an atom combine to form four new equivalent orbitals of the same energy.

Figure 3 Carbon atom in excited state

Example: Hybridization of CH4 (Methane)

In methane (CH4), the carbon atom is sp3 hybridised and each orbital overlaps with the s-orbital of each of the four hydrogen atoms.

 

Important points to remember

The different types of hybridization (sp3, sp2, sp) in carbon determines the structure and reactivity of carbon compounds that are formed. Hybridized orbitals are formed by the mixing of orbitals where electrons are mostly in an excited state. The different types of hybridization influence the bond strength and structure of the molecules