Among the triatomic molecules/ions, $\mathrm{BeCl}_2, \mathrm{~N}_3{ }^{-}, \mathrm{N}_2 \mathrm{O}, \mathrm{NO}_2{ }^{+}, \mathrm{O}_3, \mathrm{SCl}_2, \mathrm{ICl}_2{ }^{-}, \mathrm{I}_3{ }^{-}$and $\mathrm{XeF}_2$, the total number of linear molecules(s)/ion(s) where the hybridization of the central atom does not have contribution from the d-orbital(s) is [Atomic number : $\mathrm{S}=16, \mathrm{Cl}=17, \mathrm{I}=53$ and $\mathrm{Xe}=54$ ]