Question

Explain the reason behind the dimerisation of $\text{N}{\text{O}}_{\text{2}}$.

Answer 1

Structure of $\text{N}{\text{O}}_{\text{2}}$ :-

1. In $\text{N}{\text{O}}_{\text{2}}$ nitrogen atom has five valence electrons in its outermost shell.
2. Nitrogen forms a coordinate bond with oxygen by sharing two electrons.
3. The other two electrons are used with another oxygen atom to form a double bond.
4. Now only one unpaired electron is left in the nitrogen atom which makes $\text{N}{\text{O}}_{\text{2}}$ molecule highly unstable.

Reason behind the dimerisation of $\text{N}{\text{O}}_{\text{2}}$:-

1. .Due to this instability of $\text{N}{\text{O}}_{\text{2}}$because of one unpaired electron, two molecules of $\text{N}{\text{O}}_{\text{2}}$ form a dimer by combining with each other.
2. This process of forming a dimer is known as dimerization of $\text{N}{\text{O}}_{\text{2}}$.
3. Covalent bonds are formed and ${\text{N}}_2{\text{O}}_{\text{4}}$ is formed, during this dimerisation.
4. Thus as this ${\text{N}}_2{\text{O}}_{\text{4}}$ molecule does not contain any unpaired electrons it is much more stable.
5. The reaction for dimerisation of $\text{N}{\text{O}}_{\text{2}}$ is:

Therefore, due to the presence of an unpaired electron in $\text{N}{\text{O}}_{\text{2}}$, it undergoes dimerisation to form ${\text{N}}_2{\text{O}}_{\text{4}}$ and become more stable.