The number of bent-shaped molecule/s from the following is ______ N...

${N}_{3}^{-}\left(Azide\right): \overset{¯}{N} = \overset{+}{N} = \overset{¯}{N} ↔ \overset{¯}{N} - \overset{+}{N} ≡ N$

It has $sp$ hybridised central atom. Hence it is linear in shape.

${I}_{3}^{-}$(triiodide):

It has linear geometry, ${sp}^{3}d$ hybridisation with three lone pairs at central atom.

${NO}_{2}^{-}$ (nitrite) :

It is (nonlinear) bent shaped as it has ${sp}^{2}$ hybridisation with one lone pair at central atom.

${O}_{3}$ (ozone) :

It Is bent in shape with ${sp}^{2}$ hybridisation and one lone pair at central atom.

${SO}_{2}$(sulphur dioxide) :

It is bent in shape with ${sp}^{2}$ hybridisation and one lone pair at central atom.

So $3$ among the given molecules is bent in shape.