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Question: Answered & Verified by Expert
Carbon, silicon and germanium have four valence electrons each. At room temperature which one of the following statements is most appropriate?
PhysicsSemiconductorsJEE Main
Options:
  • A The number of free electrons for conduction is significant only in Si and Ge but small in C
  • B The number of free conduction electrons is significant in $\mathrm{C}$ but small in Si and $\mathrm{Ge}$
  • C The number of free conduction electrons is negligibly small in all the three
  • D The number of free electrons for conduction is significant in all three
Solution:
2290 Upvotes Verified Answer
The correct answer is: The number of free electrons for conduction is significant only in Si and Ge but small in C
Carbon (C), silicon (Si) and germanium (Ge) have the same lattice structure and their valence electrons are 4. For $\mathrm{C}$, these electrons are in the second orbit, for $\mathrm{Si}$ it is third and for germanium, it is the fourth orbit. In solid-state, the higher the orbit, the greater the possibility of overlapping of energy bands. Ionization energies are also less therefore Ge has more conductivity compared to Si. Both are semiconductors. Carbon is an insulator.

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