Among the following species, how many have trigonal bipyramidal shape ?(1) NI3 (2) I3– (3) SO32- (4) NO3–

Let us find the hybridization (H) and shape of given species.(1) For NI3, H = ½ (5+3) = 8/2 = 4 → sp3 hybridized state. It is trigonal pyramidal in shape.(2) For I3–, H = ½ (7+2+1) = 10/2 = 5 → sp3d hybridized state. It is linear in shape.(3) For SO32-, H = ½ (6+2) = 8/2 = 4 → sp3 hybridized state. It is trigonal pyramidal in shape.(4) For NO3–, H = ½ (5+1) = 6/2 = 3 → sp2 hybridized state. It is trigonal planar in shape.