See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Solution: Classification of Isomers by Spatial Arrangement **Understanding the Question:** The question asks for the term describing isomers with the same structural formula but differing in the **relative arrangement of atoms or groups in space**. **Step-by-step Analysis:** 1. **Eliminate Functional Isomers (Option 3):** These have different functional groups (e.g., ethanol vs. dimethyl ether, $C_2H_6O$). They differ in connectivity, not just spatial arrangement. ✗ 2. **Eliminate Mesomers (Option 1):** These refer to resonance structures with delocalized electrons, not spatial isomerism. ✗ 3. **Eliminate Geometrical Mesomers (Option 4):** This is not a standard classification term in chemistry. ✗ 4. **Identify Stereoisomers (Option 2):** These are isomers with: - Identical structural formulas - Same connectivity of atoms - Different spatial/3D arrangements in space Examples: *cis*-*trans* isomers (geometric), optical isomers (enantiomers) **Answer: (2) Stereoisomers** Stereoisomers perfectly match the definition—same molecular structure but different relative spatial positions of atoms/groups, which affects their chemical and physical properties.