Which of the following has the highest melting point

Options

A. Pb
B. Diamond
C. Fe
D. Na

Answer

To determine which of the given substances has the highest melting point among Pb (Lead), Fe (Iron), Na (Sodium), and Diamond, we can analyze their bonding and structure.

### Step-by-Step Solution:

1. **Identify the substances and their types of bonding:**
- **Pb (Lead)**: A metal that has metallic bonding.
- **Fe (Iron)**: A metal that also has metallic bonding.
- **Na (Sodium)**: A metal with metallic bonding.
- **Diamond**: A form of carbon that has a giant covalent structure.

2. **Understand the nature of bonding:**
- **Metallic bonding**: In metals like Pb, Fe, and Na, atoms are held together by metallic bonds, which involve a sea of delocalized electrons. The melting points of metals can vary but are generally lower than those of covalent networks.
- **Giant covalent structure**: Diamond has a three-dimensional network of covalent bonds where each carbon atom is bonded to four other carbon atoms in a tetrahedral arrangement. This extensive bonding results in a very strong structure.

3. **Compare the melting points:**
- **Lead (Pb)**: Melting point is around 327.5 °C.
- **Iron (Fe)**: Melting point is around 1538 °C.
- **Sodium (Na)**: Melting point is around 97.8 °C.
- **Diamond**: Melting point is extremely high, around 3550 °C.

4. **Conclusion:**
- Among the substances listed, Diamond has the highest melting point due to its giant covalent structure, which requires a significant amount of energy to break the strong covalent bonds.

### Final Answer:
**Diamond has the highest melting point among Pb, Fe, Na, and Diamond.**

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