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1800-102-2727Ethene (C₂H₄), also known as ethylene, is a hydrocarbon with a trigonal planar structure and a double bond between its two carbon atoms. It is a classic example of sp² hybridisation in organic chemistry.
Let us understand how hybridisation occurs in C₂H₄ and how it determines bonding and molecular shape.
Ethene consists of two carbon atoms and four hydrogen atoms. Each carbon atom forms two bonds with hydrogen atoms and one bond with the other carbon atom. To satisfy the octet rule, each carbon undergoes sp² hybridisation.
Ethene is the simplest alkene. It is an unsaturated hydrocarbon containing:
The atomic number of carbon is 6.
Ground state electronic configuration:
1s² 2s² 2p²
Only two unpaired electrons → insufficient to form four bonds.
Excited state electronic configuration:
1s² 2s¹ 2pₓ¹ 2pᵧ¹ 2p_z¹
Four unpaired electrons → sufficient to form four bonds.
Alt text: Ground state vs excited state orbital diagram
sp² hybridisation occurs when:
Each carbon atom uses:
Result:
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Alt text: Geometry and bonding of ethene
| Property | Details |
|---|---|
| Molecule | Ethene (C₂H₄) |
| Hybridisation | sp² |
| Geometry | Trigonal planar |
| Bond angle | ~120° |
| Bonding | 5 σ bonds (4 C–H, 1 C–C) and 1 π bond (C=C) |
| Unhybridised orbitals | One p orbital on each carbon for π bonding |
| Carbon valency satisfied? | Yes |
Formal charge is calculated using the formula:
Formal charge = Valence electrons − (Lone pair electrons + ½ × Bonding electrons)
Formal charge = 4 − (0 + ½ × 8) = 4 − 4 = 0
Formal charge = 1 − (0 + ½ × 2) = 1 − 1 = 0
Thus, all atoms in C₂H₄ carry zero formal charge, confirming the stability of its Lewis structure.
Each carbon atom in C₂H₄ forms four bonds: two C–H σ bonds, one C–C σ bond, and one C–C π bond. sp² hybridisation leads to trigonal planar geometry with a bond angle of approximately 120°. The π bond is responsible for the C=C double bond.
Q1. Why does carbon undergo hybridisation in C₂H₄?
To form three coplanar σ bonds and one π bond, carbon promotes an electron and mixes orbitals to form sp² hybrid orbitals.
Q2. How many σ and π bonds are present in C₂H₄?
There are 5 σ bonds and 1 π bond in ethene.
Q3. What is the shape of ethene?
Ethene has a trigonal planar shape due to sp² hybridisation on each carbon atom.
Q4. Is C₂H₄ polar or non-polar?
Ethene is non-polar because the bond dipoles cancel out due to its symmetric structure.
Q5. What are some uses of ethene?
Ethene is widely used in polyethylene and plastic production. It also plays a key role in the ripening of fruits.