Question

Which of the following exists as a covalent crystal in the solid state?

(A) Sulphur
(B) Iodine
(C) Phosphorus
(D) Silicon
Choose the correct answer from the options given below:

• A. (A) and (C) only
• B. (D) only
• C. (B) and (D) only
• D. (A), (B) and (C) only

Hint:

Covalent crystals = diamond-like structure (e.g., Silicon). Molecular solids (e.g., Iodine, Sulphur) are not covalent crystals.

Answer 1

The Correct Option is B

Step 1: Identify Solid Types.
- Covalent crystals: Characterized by atoms linked via covalent bonds, creating robust structures.
- Silicon (D): Forms a diamond-like covalent crystal structure.
- Sulphur (A): Exists as S\(_8\) molecules, constituting a molecular solid, not a covalent crystal.
- Iodine (B): Exists as I\(_2\) molecules in a molecular solid.
- Phosphorus (C): Exists in molecular form (white phosphorus), not as a covalent crystal.
Step 2: Summary.
Therefore, Silicon (D) is the only option that forms a covalent crystal.
Final Answer: \[ \boxed{\text{(D) only}} \]