Match Column I with Column II

A-3; B-4; C-2; D-1

The correct answer is option 1. A-3; B-4; C-2; D-1.

Let us delve into each of the matched pairs in detail:

A. \(PCl_5\) (Phosphorus Pentachloride): 3. Trigonal bipyramidal: \(PCl_5\) consists of a central phosphorus atom bonded to five chlorine atoms. The molecular geometry of \(PCl_5\) is trigonal bipyramidal. In this geometry, the central phosphorus atom is surrounded by three chlorine atoms in the equatorial plane and two chlorine atoms above and below the plane (axial positions), forming a trigonal bipyramid. The bond angles between the equatorial chlorine atoms are approximately 120 degrees, while the bond angles between the axial and equatorial chlorine atoms are approximately 90 degrees. The trigonal bipyramidal geometry minimizes repulsions between the electron pairs around the central atom, resulting in a stable molecular structure.

B. \(IF_7\) (Iodine Heptafluoride):4. Pentagonal bipyramidal: \(IF_7\) consists of a central iodine atom bonded to seven fluorine atoms. The molecular geometry of \(IF_7\) is pentagonal bipyramidal. In this geometry, the central iodine atom is surrounded by five fluorine atoms in the equatorial plane and two fluorine atoms above and below the plane (axial positions), forming a pentagonal bipyramid. The bond angles between the equatorial fluorine atoms are approximately 72 degrees, while the bond angles between the axial and equatorial fluorine atoms are approximately 90 degrees. The pentagonal bipyramidal geometry allows for the optimal arrangement of electron pairs, leading to a stable molecular structure.

C. \(H_3O^+\) (Hydronium Ion): 2. Pyramidal: \(H_3O^+\) consists of a central oxygen atom bonded to three hydrogen atoms. The molecular geometry of \(H_3O^+\) is pyramidal. In this geometry, the central oxygen atom is bonded to three hydrogen atoms and has one lone pair of electrons. The lone pair of electrons exerts greater repulsion than the bonding pairs, causing the hydrogen atoms to be pushed slightly downward, resulting in a pyramidal shape. The bond angle between the hydrogen atoms is approximately 107 degrees, slightly less than the ideal tetrahedral angle of 109.5 degrees due to the lone pair-bonding pair repulsion.

D. \(ClO_2\) (Chlorine Dioxide): 1. Angular: \(ClO_2\) consists of a central chlorine atom bonded to two oxygen atoms. The molecular geometry of \(ClO_2\) is angular or bent. In this geometry, the central chlorine atom is bonded to two oxygen atoms, with the two oxygen-chlorine bonds oriented at an angle to each other. The lone pair of electrons on the central chlorine atom repels the bonding electron pairs, resulting in a bent or angular shape. The bond angle between the two oxygen-chlorine bonds is approximately 117 degrees.

These explanations illustrate how the molecular geometries of each compound arise from the arrangement of atoms and lone pairs around the central atom, as well as the influence of electron repulsions on the bond angles. Each geometry represents the most stable arrangement of electron pairs, minimizing repulsions and resulting in a stable molecular structure.