Which of the following covalent solid is the conductor of electricity ?

Options

A. SiC
B. AlN
C. Diamond
D. Graphite

Answer

To determine which covalent solid is a conductor of electricity, we need to analyze the properties of various covalent solids and their ability to conduct electricity. Here’s a step-by-step solution:

### Step 1: Understand the Concept of Covalent Solids
Covalent solids are characterized by a network of covalent bonds forming a giant structure. They typically do not have free electrons, which are necessary for conducting electricity.

**Hint:** Remember that for a substance to conduct electricity, it must have free-moving charged particles (like electrons or ions).

### Step 2: Analyze the Given Covalent Solids
1. **Silicon Carbide (SiC)**: This is a covalent solid with a strong covalent network. It does not have free electrons, thus it does not conduct electricity.

2. **Aluminum Nitride (AlN)**: This is also a covalent solid. It consists of covalent bonds between aluminum and nitrogen. Similar to SiC, it lacks free electrons and does not conduct electricity.

3. **Diamond**: Diamond is a form of carbon where each carbon atom is bonded to four other carbon atoms in a tetrahedral structure. This structure is very rigid and does not allow for free movement of electrons, hence diamond does not conduct electricity.

4. **Graphite**: Graphite, another allotrope of carbon, has a layered structure where each carbon atom is bonded to three others in a hexagonal arrangement. The fourth electron of each carbon atom is free to move between the layers, allowing graphite to conduct electricity.

**Hint:** Compare the structures of these solids and identify which one has free-moving electrons.

### Step 3: Conclusion
Among the covalent solids analyzed, **graphite** is the only one that can conduct electricity due to the presence of free electrons that can move within its layered structure.

**Final Answer:** The covalent solid that is a conductor of electricity is **Graphite**.