how to find the bond order in NO2- and NO3- . pls explain.

For compounds with resonance structures, to find the bond order the number of resonance structures and bonding pairs must be taken into account.

In nitrite ion, NO2-, there are two equivalent resonance structures.

We cannot say that the bonds between N-O are single or double. Hence we consider NO2- has two equivalent NO bonds where three pairs of bonding electrons are distributed over two equivalent NO bond locations. Hence to describe the bonding in the resonance hybrid we consider the

fractional bond order = total no. of NO boding pairs/no.of NO bond locations

  = 3/2

   = 1.5

Each N-O bond order in NO2- is 1.5.

Similarly in nitrate ion, NO3-, there are three equivalent resonance structures.

NO3- has three equivalent NO bonds where four pairs of bonding electrons are distributed over three equivalent NO bond locations. Hence the

fractional bond order = total no. of NO boding pairs/no.of NO bond locations

  = 4/3

  = 1.3

Each N-O bond order in NO3- is 1.3.

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