Question

What is the hybridisation of ${C_2}{H_4}$ . Draw its structure also.

Answer 1

The common name of alkenes is alkylene with the general formula ${C_n}{H_{2n}}$ , containing double bonds between the carbon atoms. Alkenes are also called unsaturated hydrocarbons. Alkenes are usually $s{p^2}$ hybridized with a planar geometry. Ethylene or ethene is the simplest alkene.

Complete answer:
${C_2}{H_4}$ has $s{p^2}$ hybridization.
${C_2}{H_4}$ has $2$ carbon molecule and $4$ hydrogen molecule, each carbon atom is attached to other carbon by double bond and singly bonded to the hydrogen atom.
Ground state electronic configuration of carbon is $1{s^2}{\text{ 2}}{{\text{s}}^2}{\text{ 2}}{{\text{p}}^2}$ . Because of the approach of hydrogen atom carbon acquires the electronic configuration $1{s^2}{\text{ }}2{s^1}{\text{ }}2p_x^1{\text{ }}2p_y^1{\text{ }}2p_z^1$ but only $1s$ and $2p$ orbital will take part in hybridization. Ethene has $3s{p^2}$ hybridized; this results in formation of orbitals.
One electron from $2{s^2}$ orbital moves to $2{p_z}$ orbital.
$s{p^2}$ hybrid orbital of one carbon overlaps with $s{p^2}$ hybrid orbital of second carbon atom and results in $s{p^2} - s{p^2}$ overlap (sigma overlap) and the two $s{p^2}$ hybrid orbitals is head on overlapped by two hydrogen atom which has unpaired electrons. So now total $5$ sigma bonds.
There is still one $p$ -orbital that has an unpaired electron, in each of the carbon atom there is one $p$ -orbital that is unhybridized so now there will be overlap between the $2$ lobes of unhybridized $p$ -orbital and hence one pi bond will be formed.

Around each of the carbon atoms the bond angle is near to ${120^\circ }$ . ${117.4^\circ }$ is the $H - C - H$ angle and the shape thus formed is trigonal planar.

Note:
Ethylene is a growth hormone that affects the ripening and flowering in plants. Ethylene contains one pi bond and five sigma bonds. Ethylene mostly undergoes electrophilic substitution reactions. Ethylene is used in industrial reactions such as polymerization, oxidation, and halogenation, etc.