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Carbon, silicon, and germanium each possess four valence electrons. At room temperature, which statement best describes their conduction electrons?

1. The concentration of free electrons available for conduction is appreciable in Si and Ge, but very low in C.
2. The concentration of free conduction electrons is appreciable in C, but very low in Si and Ge.
3. The concentration of free conduction electrons is negligibly small in all three.
4. The concentration of free electrons available for conduction is appreciable in all three.

Correct answer: The concentration of free electrons available for conduction is appreciable in Si and Ge, but very low in C.

Solution

Silicon and germanium are semiconductors that can generate free electrons at room temperature, allowing for appreciable conduction, while carbon, in its common forms like graphite or diamond, has a much lower concentration of free electrons, making it less effective for conduction.

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