Concept: Isostructural Species

Isostructural species are molecules or ions that have the same shape and hybridization. To determine if molecules are isostructural, we need to analyze their central atom's hybridization and the arrangement of atoms around it, which is often determined by VSEPR theory.

Why C is correct:

Let's analyze the structure and hybridization of each molecule:

• ${\mathrm{CO}}_2$ (Carbon Dioxide): The central atom is carbon. Carbon forms two double bonds with two oxygen atoms. There are no lone pairs on the central carbon atom. The steric number is 2 (2 bonding pairs + 0 lone pairs), leading to sp hybridization and a linear geometry with a bond angle of 180°.
• A) ${\mathrm{SO}}_2$ (Sulfur Dioxide): The central atom is sulfur. Sulfur forms two bonds with two oxygen atoms and has one lone pair. The steric number is 3 (2 bonding pairs + 1 lone pair), leading to sp² hybridization and a bent (V-shaped) geometry.
• B) ${\mathrm{NO}}_2$ (Nitrogen Dioxide): The central atom is nitrogen. Nitrogen forms two bonds with two oxygen atoms and has one unpaired electron (radical). The steric number is effectively 2.5, leading to sp² hybridization and a bent geometry.
• C) ${\mathrm{C}}_2{\mathrm{H}}_2$ (Ethyne or Acetylene): This molecule has two central carbon atoms. Each carbon atom is bonded to one hydrogen atom and triple-bonded to the other carbon atom. Each carbon atom has a steric number of 2 (1 C-H bond + 1 C≡C bond), leading to sp hybridization. The molecule is linear. Since both ${\mathrm{CO}}_2$ and ${\mathrm{C}}_2{\mathrm{H}}_2$ are linear and sp hybridized, they are isostructural.
• D) ${\mathrm{SnCl}}_2$ (Tin(II) Chloride): The central atom is tin. Tin forms two bonds with two chlorine atoms and has one lone pair. The steric number is 3 (2 bonding pairs + 1 lone pair), leading to sp² hybridization and a bent (V-shaped) geometry.

Therefore, ${\mathrm{CO}}_2$ is isostructural with ${\mathrm{C}}_2{\mathrm{H}}_2$.

Correct Answer: (C)