CBSE Class 12-science Answered

In the NO molecule there are 11 valency 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.

The above structure accounts for one odd unpaired electron in NO. But dimeric form of this 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 dimerization 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.