Understanding Hybridisation of Carbon

Hybridisation is the process by which atomic orbitals mix to create new orbitals of equal energy, and considering this process, molecular shape and bonding behaviour are also determined. Carbon forms stable covalent bonds with multiple elements due to its capacity to hybridise atomic orbitals.

Hence, understanding carbon hybridisation is essential to know about the structure and reactivity of many molecules

Understanding Electronic Configuration and the Concept of Hybridisation

In the ground state of carbon: 1s² 2s² 2p² (2s orbital has 2 electrons and the p orbital has 2 unpaired electrons)

In order for the carbon to go into an excited state, it has to form 4 covalent bonds. Hence, 1 electron in the 2s orbital is excited and goes to the empty 2p orbital, hence creating four unpaired electrons for bond formation.

Ground state vs excited state orbital diagram

By mixing these valence orbitals (2s and 2p), hybrid orbitals are formed, and hybridisation then occurs. The molecular geometry and bond angle are then influenced depending on the type of hybridisation which occurs. The type of hybridisation depends on the number and nature of the bonds carbon forms.

Types of Carbon Hybridisation

Let us understand the different types of hybridisation in carbon.

1. sp³ Hybridisation

When carbon forms four single sigma (σ) bonds, this type of hybridisation occurs. E.g.: alkanes
Four equivalent sp³ hybrid orbitals are formed when one s orbital mixes with three p orbitals.
Shape: Tetrahedral
Bond Angle: 109.5° (in order to minimise repulsion)
Eg : methane (CH₄), ethane (C₂H₆), propane (C₃H₈)

2. sp² Hybridization

When carbon forms double bonds, this type of hybridisation occurs. E.g.: alkenes
Three equivalent sp² hybrid orbitals are formed when one s orbital mixes with two p orbitals.
A pi (π) bond is formed with the remaining one unhybridized p orbital.
Shape: Trigonal planar
Bond Angle: 120°
Eg : ethylene (C₂H₄), benzene (C₆H₆)

3. sp Hybridization

When carbon either forms a triple bond or when an atom is bonded to two other atoms, this type of hybridisation occurs. E.g.: acetylene (C₂H₂)
Two equivalent sp hybrid orbitals are formed when one s orbital mixes with one p orbital, which are aligned linearly.
Two pi (π) bonds are formed with the remaining two unhybridized p orbitals.
Shape: Linear
Bond Angle: 180°
E.g.: acetylene (C₂H₂)

Details At A Glance

Hybridization	Orbitals Mixed	Number of Hybrid Orbitals	Bonding Type	Geometry	Bond Angle	Example
sp³	1 s + 3 p	4	4 σ bonds	Tetrahedral	109.5°	Methane (CH₄)
sp²	1 s + 2 p	3	3 σ + 1 π bond	Trigonal planar	120°	Ethylene (C₂H₄)
sp	1 s + 1 p	2	2 σ + 2 π bonds	Linear	180°	Acetylene (C₂H₂)

Importance and Applications

Hybridisation has various important applications in organic chemistry. It explains the behaviours seen in fuels, polymers, biological molecules, etc., by physical and chemical properties such as bond strength, polarity, and reactivity, which are influenced by hybridisation.

Summing Up

Carbon is very important for both living things and in making new materials in chemistry since it can change bonding shapes. In all, hybridisation helps us understand how carbon forms different types of bonds. In alkanes, carbon typically has sp³ hybridisation, which gives a tetrahedral shape. Similarly, in sp² it gives a trigonal planar shape and in sp it gives a linear shape.