Q177 / 180 · COMEDK 2025 (10 May Shift 2) · Physics
Diamond is considered as an insulator because
- Correct answerADiamond has very large forbidden energy gap.
- BRefractive index of diamond is very low
- CIn the diamond the carbon atoms are held by weak covalent bonds
- DValance band and conduction band of diamond are overlapping
Solution
Diamond is an allotrope of carbon where each carbon atom is sp$^{3}$ hybridized and forms four strong covalent bonds with neighboring carbon atoms. This structure results in a rigid, three-dimensional network.
In terms of band theory, the valence electrons are tightly bound in these covalent bonds. The energy required to excite an electron from the valence band to the conduction band is the forbidden energy gap (band gap).
For diamond, this band gap is approximately $5.5$ eV, which is significantly large. Because of this large energy gap, electrons cannot easily jump from the valence band to the conduction band at room temperature, making diamond an electrical insulator.
Answer: Diamond has very large forbidden energy gap.
In terms of band theory, the valence electrons are tightly bound in these covalent bonds. The energy required to excite an electron from the valence band to the conduction band is the forbidden energy gap (band gap).
For diamond, this band gap is approximately $5.5$ eV, which is significantly large. Because of this large energy gap, electrons cannot easily jump from the valence band to the conduction band at room temperature, making diamond an electrical insulator.
Answer: Diamond has very large forbidden energy gap.
Hence, the correct answer is option: 'A'.