Choose the correct sequence of the following materials on the basis o…

The correct answer is Option (2) → (D), (B), (C), (A)

The energy band gap is the gap between the top of the valence band and the bottom of the conduction band. It is large for insulators, small for semiconductors and zero for metals.

    \( \text{(D) Carbon (Diamond): about 5.4 eV (insulator)} \)
    \( \text{(B) Silicon: about 1.1 eV} \)
    \( \text{(C) Germanium: about 0.7 eV} \)
    \( \text{(A) Copper: 0 (bands overlap; a metal)} \)

Decreasing order of band gap:

    \( \text{(D)} \gt \text{(B)} \gt \text{(C)} \gt \text{(A)} \)

NCERT (2026-27):
Classification of Metals, Conductors and Semiconductors – “… Normally the conduction band is empty. But when it overlaps on the valence band electrons can move freely into it. This is the case with metallic conductors.”

Extrinsic Semiconductor – “… For C (diamond), Si and Ge, the energy gaps are 5.4 eV, 1.1 eV and 0.7 eV, respectively.”