Question

what is hybradisation why does it occur? how carbon is sp3 hybradization

Answer 1

I may not be the best at explaining this because this is a difficult concept to explain since it is a very complex topic in general, but, basically it's a concept of mixing atomic orbitals into new hybrid orbitals. they help in assessing molecular orbital geometry and bonding of molecules.
In your example, carbon is sp\(^3\) because it's 2s and all three of its 3p orbitals can hybridize to form four sp3 orbitals. If they bond, for example, with hydrogen, to form methane, then, these orbitals then bond with four hydrogen atoms through sp3-s orbital overlap. If you look at the molecule, methane, you will see it forms a tetrahedral geometry. What this means is that the 2s orbitals and all three of the 2p orbitals hybridize to form four sp orbitals, each consisting of 75% p character and 25% s character.