Arrange the following in the increasing order of their energy gap between their conduction and valence bands:
(A) Si
(B) C (diamond)
(C) Ge
(D) Sn
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (D), (C), (A), (B)
These four elements are in the same group of the periodic table. As the atoms get larger down the group, the energy gap between the valence band and the conduction band becomes smaller.
\( (A)\ \mathrm{Si}: E_{g} \approx 1.1\,\mathrm{eV} \)
\( (B)\ \mathrm{C\ (diamond)}: E_{g} \approx 5.4\,\mathrm{eV} \)
\( (C)\ \mathrm{Ge}: E_{g} \approx 0.7\,\mathrm{eV} \)
\( (D)\ \mathrm{Sn}: E_{g} \approx 0\,\mathrm{eV} \)
Tin is taken as essentially metallic, with a gap close to zero. The increasing order of energy gap is therefore Sn \( \lt \) Ge \( \lt \) Si \( \lt \) C, that is (D), (C), (A), (B).
NCERT (2026-27):
Extrinsic Semiconductor – “… The difference in the resistivity of C, Si and Ge depends upon the energy gap between their conduction and valence bands. For C (diamond), Si and Ge, the energy gaps are 5.4 eV, 1.1 eV and 0.7 eV, respectively. Sn also is a group IV element but it is a metal because the energy gap in its case is 0 eV.”