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: Understand types of solids.
- Covalent crystals: Atoms are held together by covalent bonds, resulting in a very strong structure.
- Silicon (D): Forms a covalent crystal structure (diamond-like).
- Sulphur (A): Exists as S\(_8\) molecules in 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: Conclusion.
Thus, only Silicon (D) forms a covalent crystal.
Final Answer: \[ \boxed{\text{(D) only}} \]