Show how a double and triple bond are formed between carbon atoms in
`C_(2)H_(4)` and

Explanation

`C_(2)H_(4)` (Ethylene) : In the formation of ethylene molecule, the two carbon atoms will undergo `sp^(2)` hybridisation in their excited states. As a result of which `sp^(2)` hybrid orbitals will form on each each of them. All the six hybrid orbitals contain an electron, each. At first, one `sp^2` hybrid orbital of each carbon atom overlap Head-Head forming one sigma bond in between them. Now, the remaining four `sp^(2)` hybrid orbitals overlap Head-Head with '1s' orbitals of four 'H' atoms forming four sigma bonds. Now, the unhybridised pure `2p_(z)` orbitals of each carbon atom overlap side-wise forming `pi` bond in between them. Thus a double bond is formed in between the two carbon atoms.
In total there are five sigma bonds and one pi bond in ethylene molecule. The molecule as a whole is planar.