Question

Diamond is considered as an insulator because

• A. Diamond has very large forbidden energy gap.
• B. Valance band and conduction band of diamond are overlapping.
• C. In the diamond the carbon atoms are held by weak covalent bonds
• D. Refractive index of diamond is very low

Hint:

Large band gap \( \Rightarrow \) insulator, small gap \( \Rightarrow \) semiconductor.

Answer 1

The Correct Option is A

Step 1: Understand band theory.
Electrical conduction depends on the energy gap between valence band and conduction band.

Step 2: Define insulator.
In insulators, the forbidden energy gap is very large.

Step 3: Property of diamond.
Diamond has a very large band gap (~5.5 eV).

Step 4: Effect on electrons.
Electrons cannot easily jump from valence to conduction band.

Step 5: Resulting behavior.
Hence, diamond does not conduct electricity.

Step 6: Reject incorrect options.
- Overlapping bands indicate conductor.
- Bonds in diamond are strong, not weak.
- Refractive index is unrelated to conduction.

Step 7: Final Answer.
\[ \boxed{\text{Option (A)}} \]