The geometrical arrangement of orbitals and shape of I3^- are respectively : — Chemical Bonding Chemistry Question

💡 Solution & Explanation

Step 1: Calculate the steric number of the central Iodine in the triiodide ion (I3^-). The central Iodine atom has 7 valence electrons, plus 1 for the negative charge = 8. Two electrons form single bonds with the terminal Iodine atoms, leaving 6 non-bonding electrons (3 lone pairs). Steric number = 2 bond pairs + 3 lone pairs = 5. Step 2: A steric number of 5 corresponds to sp3d hybridization, which has a trigonal bipyramidal (TBP) orbital arrangement. Step 3: To minimize repulsions, the 3 lone pairs occupy the equatorial positions of the TBP, leaving the 2 bonding atoms in axial positions, which results in a linear shape. This corresponds to option (a).