The mixing of one s-orbital and three p- orbitals of the same atom having nearly the same energy to form four orbitals of equal in all respects and tetrahedrally arranged is known as sp3 hybridization.
sp3 hybridized orbitals repel each other and they are directed to four corners of a regular tetrahedron. The angle between them is 109.5° and geometry of the molecule is tetrahedral (non-planar). This type of hybridization is also known as tetrahedral hybridization.
The sp2 hybridization is shown pictorially in the figure.
Formation of Methane Molecule (CH4):
Step -1: Formation of the excited state of a Carbon atom:
The carbon atom in the ground state takes up some energy and goes to the excited state. In this process, a pair of electrons in 2s orbital splits up and one of the electron from this pair is transferred to empty 2pz orbital. Thus the excited state has four half filled orbitals.
Step – 2: Hybridization of Orbitals:
One orbital of 2s and three orbitals of 2p mix up forming four hybrid orbitals of equivalent energy. These four new equivalent orbitals are called sp3 hybrid orbitals. They are identical in all respect.
Angle and Geometry:
Four sp3 hybridized orbitals formed, repel each other and they are directed towards the four corners of a regular tetrahedron. The Angle between them is 109.5°.
Each sp3 hybrid orbital contains one unpaired electron.
In each sp3 hybrid orbital, one of the lobes is bigger because of more concentration of electron density. Only bigger lobe is involved in bond formation. Due to this maximum overlapping is achieved.
Four sp3 hybrid orbitals of carbon atom having one unpaired electron each overlap separately with 1s orbitals of four hydrogen atom along the axis forming four covalent bonds
Thus in CH4 molecule has a tetrahedral structure with a carbon atom at the centre and four hydrogens at the four corners of a regular tetrahedron. H-C-H bond angle is 109.5°.
Four sp3 hybrid orbitals of carbon atom having one unpaired electron each overlap separately with 1s orbitals of four hydrogen atom along the axis forming four covalent bonds (sigma bonds).
The bonds between carbon and hydrogen are sp3– s.
Thus H – C — H bond angles are 109.5°. The molecule is tetrahedral.