Find the number of planar chemical species in which $d_{z_2}$ orbital of the underlined atom z participate in bonding ${\underset{\_}{\mathrm{O}}}_3,{\underset{\_}{\mathrm{SF}}}_4,{\underset{\_}{\mathrm{SNF}}}_3,{\underset{\_}{\mathrm{SOF}}}_4,{\underset{\_}{I}}_3^{-},{\mathrm{ICl}}_3$

The central iodine will have three lone pairs because three orbitals are fully filled. As a result, the lone pair of electrons occupy the equatorial plane, while the bond pairs occupy the axial plane. As a result of the bond pairs being present in the same plane, we can say ${\mathrm{I}}_3^{-}$  is planar. The planar chemical species in which $d_{z_2}$ orbital of the underlined atom z participate in bonding are,

${\mathrm{I}}_3^{-},{\mathrm{ICl}}_3$