The `C-C` bond length in diamond is `"………….."`while in graphite it is `"………….."`.

Answer

To determine the bond lengths of the carbon-carbon (C-C) bonds in diamond and graphite, we can analyze the hybridization and bonding characteristics of each structure.

### Step-by-Step Solution:

1. **Identify the Structure of Diamond**:
- Diamond has a tetrahedral structure where each carbon atom is sp³ hybridized.
- In this structure, each carbon forms four single bonds with other carbon atoms.

2. **Determine the C-C Bond Length in Diamond**:
- The C-C bond length in diamond is primarily due to single bonds with no double bond character.
- The bond length in diamond is approximately **154 picometers**.

3. **Identify the Structure of Graphite**:
- Graphite has a planar structure where each carbon atom is sp² hybridized.
- In graphite, each carbon atom forms three sigma bonds with neighboring carbon atoms and has one unhybridized p orbital that can participate in π bonding, leading to double bond character.

4. **Determine the C-C Bond Length in Graphite**:
- The presence of double bond character in graphite increases the bond order, which decreases the bond length.
- The C-C bond length in graphite is approximately **141.5 picometers**.

5. **Conclusion**:
- Therefore, the C-C bond length in diamond is **154 picometers**, while in graphite it is **141.5 picometers**.

### Final Answer:
- The C-C bond length in diamond is **154 picometers** while in graphite it is **141.5 picometers**.