Which of the following is not a crystalline solid?

Options

A. `KCl`
B. `CsCl`
C. Glass
D. Rhombic S

Answer

To determine which of the following options is not a crystalline solid, we need to understand the characteristics of crystalline and amorphous solids.

### Step-by-Step Solution:

1. **Understand the Definition of Crystalline Solids**:
- Crystalline solids are materials whose constituents (atoms, molecules, or ions) are arranged in a highly ordered and repeating pattern. This orderly arrangement leads to distinct geometric shapes and well-defined melting points.

2. **Analyze the Given Options**:
- The options provided are:
- KCl (Potassium Chloride)
- CSCl (Cesium Chloride)
- Glass
- Rhombic Sulfur

3. **Evaluate Each Option**:
- **KCl**: This is an ionic compound and forms a crystalline structure with a regular arrangement of ions.
- **CSCl**: Similar to KCl, cesium chloride is also an ionic compound that forms a crystalline lattice.
- **Rhombic Sulfur**: This is a form of sulfur that has a crystalline structure, characterized by a specific arrangement of sulfur atoms.
- **Glass**: Glass is known to be an amorphous solid. It lacks a long-range order in its atomic arrangement, meaning its structure is not repetitive or organized in a specific pattern.

4. **Identify the Non-Crystalline Solid**:
- Among the options, KCl, CSCl, and rhombic sulfur are all crystalline solids. However, glass does not have a crystalline structure and is classified as an amorphous solid.

5. **Conclusion**:
- The correct answer is **glass**, as it is not a crystalline solid.

### Final Answer:
**Glass is not a crystalline solid.**

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