Q: Which of the following is not a crystalline solid?

Explanation:

Crystalline Solids

Crystalline solids are characterized by a highly ordered and repeating arrangement of their constituent particles, such as atoms, ions, or molecules, extending in all three spatial dimensions. This long-range order gives crystalline solids well-defined geometric shapes and distinct melting points.

Let’s examine each option:

Option A: KCl (Potassium Chloride) – This is an ionic compound that forms a crystalline lattice structure. The potassium and chloride ions are arranged in a regular, repeating pattern, typical of crystalline solids.

Option B: CsCl (Cesium Chloride) – Similar to KCl, cesium chloride forms a crystalline structure. The cesium and chloride ions are organized in a specific, orderly lattice arrangement, which is a hallmark of crystalline materials.

Option D: Rhombic S (Rhombic Sulfur) – Rhombic sulfur is one of the allotropes of sulfur and has a crystalline structure. Its molecules are arranged in an orderly, repeating pattern, characteristic of crystalline solids.

Option C: Glass – Unlike the other options, glass does not have a long-range ordered structure. It is an amorphous solid, meaning its molecules are arranged more randomly without a repeating pattern. This lack of orderly structure means glass does not form crystals and does not exhibit the sharp melting points typical of crystalline solids.

Therefore, Glass is not a crystalline solid because it lacks the long-range ordered arrangement of particles that defines crystalline materials.