Why NO does not dimerise even it has odd electron?

Asked by ranvirsingh1as | 16th Dec, 2018, 10:47: PM

Expert Answer:

In the NO molecule, there are 11 valence electrons having a set of 5 electrons of one spin and 6 electrons of the opposite spin. 
Both the sets have a tetrahedral orientation around the two atoms.
But the dimeric form of NO molecule is not possible due to the following reasons:
  1. As per the thermodynamic point of view, entropy is in favour of small molecules,
  2. Dimerisation takes place if there is some gain in bonding. But in the dimerisation of NO, there is no gain of electrons because the bond order of 2 ½ remains the same in the dimer.
  3. Hence, the dimer is unstable relative to the monomer in case of NO.

Answered by Ramandeep | 17th Dec, 2018, 11:03: AM