Explain the shape of `I_(3)^(-)` ion .

Explanation

The central I atom has the outer shell electronic configuration in the ground
state as ` 5s^(2) 5p_(x)^(2) 5p_(y)^(2) p_(z)^(1) 5d^(0) ` . It undergoes ` sp^(3)` d hydridisation . Out of the
five ` sp^(3) d` hydrid orbitals , one in half-filled , one is empty and the remaining
there are fully-filled . The half-filled froms covalent bond with iodine atom
The empty orbital accepts electron pair from `I^(-)` ion to from a coordinate bond
The remaining three fully-filled occupy equatorial positions. Thus , the geometry
of three lone pairs and two bond pairs is trigonal bipyramidal and the shape
of `I_(3)^(-)` is linear as shown in the Fig .
Similarly , the shapes of `ICl_(2)^(-) and [I Br F]^(-)` are also linear .