Among the following highest melting point is associated with

Options

A. a) `NaCl_((s))`
B. b) Graphite
C. c) `P_(4)`
D. d) K

Answer

To determine which of the given solids has the highest melting point, we need to analyze the types of solids presented in the options and their respective melting points.

### Step-by-Step Solution:

1. **Identify the Types of Solids**:
- **Option A: NaCl (Sodium Chloride)** - This is an ionic solid.
- **Option B: Graphite** - This is a covalent solid (also known as a network solid).
- **Option C: C4 (Tetrahedral Carbon)** - This is a molecular solid.
- **Option D: Potassium (K)** - This is a metallic solid.

2. **Understand Melting Points of Different Types of Solids**:
- **Ionic Solids** (like NaCl): Typically have medium to high melting points due to the strong electrostatic forces between the ions. However, they are not the highest.
- **Covalent Solids** (like Graphite): Have very high melting points because of the strong covalent bonds that extend throughout the structure.
- **Molecular Solids** (like C4): Generally have low melting points as they are held together by weaker van der Waals forces.
- **Metallic Solids** (like Potassium): Have melting points that can vary widely, typically between low to high, but generally lower than covalent solids.

3. **Compare the Melting Points**:
- Among the options, covalent solids (like graphite) are known for their exceptionally high melting points, often exceeding those of ionic and metallic solids.
- Ionic solids like NaCl have lower melting points compared to covalent solids.
- Molecular solids have the lowest melting points.
- Metallic solids can have variable melting points, but they do not reach the levels of covalent solids.

4. **Conclusion**:
- Based on the analysis, the solid with the highest melting point among the options provided is **Graphite** (Option B).

### Final Answer:
The solid with the highest melting point is **Graphite (Option B)**.

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