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

Options

A. The number of free conduction electrons is neglibly small in all the three
B. The number of free electrons for conduction is significant in all the three
C. The number of free electrons for conduction is significant only in Si and Ge but small in C
D. The number of free electrons for conduction is significant in C but small in Si and Ge

Answer

To analyze the behavior of carbon, silicon, and germanium at room temperature regarding their valence electrons and conductivity, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Valence Electrons**:
- All three elements (carbon, silicon, and germanium) have four valence electrons.

2. **Understand the Bonding in Carbon**:
- Carbon atoms are strongly covalently bonded due to their high catenation property. This means that the bonds between carbon atoms are very stable and do not allow for free electrons to move around.
- **Conclusion**: At room temperature, carbon has negligible or no free electrons.

3. **Analyze Silicon's Properties**:
- Silicon also has four valence electrons, but it has a lower catenation property compared to carbon. The bonds in silicon are not as strong, allowing some electrons to become free.
- **Conclusion**: At room temperature, silicon has a significant number of free electrons available for conduction.

4. **Evaluate Germanium's Characteristics**:
- Germanium has a larger atomic size than silicon, which results in weaker bonding. This allows more electrons to break free from their bonds.
- **Conclusion**: At room temperature, germanium has a large number of free electrons available for conduction.

5. **Compare the Free Electrons in All Three Elements**:
- Carbon: negligible free electrons.
- Silicon: significant free electrons.
- Germanium: large number of free electrons.

6. **Select the Most Appropriate Statement**:
- From the analysis, we can evaluate the options:
- Option 1: The number of free electrons is negligible or none in all three. (Incorrect)
- Option 2: The number of free electrons for conduction is significant in all three. (Incorrect)
- Option 3: The number of free electrons for conduction is significant only in silicon and germanium but small in carbon. (Correct)
- Option 4: The number of free electrons for conduction is significant in carbon but small in silicon and germanium. (Incorrect)

### Final Answer:
The most appropriate statement is **Option 3**: The number of free electrons for conduction is significant only in silicon and germanium but small in carbon.