Hybridisation of Ethene

When two atomic orbitals combine to form a new orbital, the process is known as hybridisation. The individual orbitals redistribute their energies and give new orbitals the same energy. The new orbital thus formed is known as a hybrid orbital. These hybrid orbitals could be used to describe the atomic bonding properties and molecular geometry. Atomic orbitals that have the same level of energy perform hybridisation. The hybridisation of Ethene is an sp2 hybridisation, which means it is formed as a result of a combination of one s and two p orbitals, and three sp2 hybrid orbitals are formed. Another name for sp2 hybridisation is trigonal hybridisation.

Types of hybridisation

• sp hybridisation

When an s orbital combines with a p orbital and two new hybrid orbitals are formed, this type of hybridisation is known as sp hybridisation. It results in the formation of linear molecules with a bond angle of 80 degrees. The other name for sp hybridisation is diagonal hybridisation. The new orbitals share an equal amount of s and p features.

• sp2 hybridisation

In this type of hybridisation, one s and two p orbitals combine and form three hybrid orbitals. The three hybrid orbitals have trigonal planar geometry with 120 degrees angles between them. All the orbitals created share 33.33% s character and 66.66% p character. The new orbitals produced are known as sp2 hybrid orbitals. Compounds of boron are examples of such a type of hybridisation.

• sp3 hybridisation

In sp3 hybridisation, one s and three p orbitals fuse to form four sp3 hybrid orbitals. It is also called tetrahedral hybridisation. They form an angle of 109.28 degrees with each other and are pointed towards the four corners of a regular tetrahedron.

• sp3d hybridisation

In sp3d hybridisation, one s, three p, and one d orbitals are combined, resulting in the formation of five sp3d orbitals with equivalent energy. The resultant orbital has trigonal bipyramidal symmetry. Three hybrid orbitals are slanted towards each other at an angle of 120 degrees. The remaining two are inclined at 90 degrees angles and are also known as axial orbitals.

• sp3d2 hybridisation

Six hybrid orbitals are formed by one s, three p, two d orbitals. They slant toward each other at an angle of 90 degrees and are pointed towards the corners of the octahedron.

Hybridisation of ethene

The hybridisation of ethene falls under sp2 hybridisation. Here, one s orbital and two p orbitals are mixed to form three sp2 hybrid orbitals. The three orbitals formed have the same shape and level of energy. Each hybrid orbital thus formed has 1/3rd character of s and 2/3rd character of p. These orbitals are inclined at an angle of 120 degrees and have trigonal planar geometry. Ethene consists of 2 CH and 4 H molecules. Ethene makes a double bond between the carbon atoms.

To form the required number of bonds, the carbon atom has to give one of the 2s2 pairs into the 2pz orbital. When CH2=CH2 bonds are formed, the carbon atom gets into an excited state, needing only one electron to form bonds. To accomplish that, an electron from 2s2 orbitals shifts to the 2pz orbitals to provide four unpaired electrons. When carbon is in its ground state, it has an electronic configuration of (1s2 2s2 2p1 2p1). However, in an excited state, its configuration changes to (1s2 2s1 2px12py1 2pz1).

Shape of ethene

The sp2 orbitals determine the geometry of ethene. All these orbitals lie in the same plane and the p orbital is at a right angle. After the building of bonds, all the sigma bonds within the molecule need to lie in the same plane as well. If there is any twist in the molecule, it could mean that neither the orbitals are parallel to each other nor are they touching, which could cause the pi bond to break. Ethene is said to be a planar molecule.

The sp2 orbitals lie at 120° angle towards each other. It is possible to have a slight alteration, as two hydrogens and one carbon atom are linked to each carbon atom.

Conclusion:

Hybridisation is the phenomenon of joining two orbitals that redistribute the energy of their individual atoms to form new types of orbitals with similar energy levels and shapes. These newly formed orbitals are known as hybrid orbitals. During hybridisation, the orbitals are mixed instead of electrons. Thus, completely filled, half-filled, or even empty orbitals can take part in hybridisation. Every hybrid orbital has two lobes – a large and a small lobe. Bonds are made using the large lobe. The hybridisation of ethene is an sp2 hybridisation. It uses one s orbital and two p orbitals to form the hybrid orbital.