Carbon, silicon and germanium have four valence electrons e…

Physics Semiconductor Electronics Semiconductors MCQ (Single Correct)

Carbon, silicon and germanium have four valence electrons each. At room temperature which one of the following statements is most appropriate?

the number of free conduction electrons is significant in C but small in Si and Ge

the number of free conduction electrons is negligibly small in all the three.

the number of free electrons for conduction is significant in all the three.

the number of free electrons for conduction is significant only in Si and Ge but small in C.

Text Solution

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The correct answer is:

, Si and Ge have the same lattice structure and their valence electrons are 4 .
For , these electrons are in the second orbit, for it is third and germanium it is the fourth orbit. In solid state, higher the orbit, greater the possibility of overlapping of energy bands.
lonization energies are also less therefore has more conductivity compared to .
Both are semiconductors. Carbon is an insulator.