Which of the following is not the property of interstitial compound

Options

A. They have high M.P, higher than those of pure metals
B. They are very hard, some borides approach diamond in hardness.
C. They retain metallic conductivity
D. Their chemical reactivity is very high

Answer

To determine which of the following is not a property of interstitial compounds, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Interstitial Compounds**:
Interstitial compounds are formed when small atoms (like carbon, nitrogen, or boron) occupy the interstitial spaces (gaps) between the larger metal atoms in a metallic lattice. This can significantly alter the properties of the metal.

2. **Analyzing the Options**:
- **Option A: They have high melting points higher than those of pure metals.**
- Interstitial compounds typically have high melting points due to the strong bonding between the small atoms and the metal lattice.
- **Option B: They are very hard. Some borides approach diamond in hardness.**
- Interstitial compounds are known for their hardness. For example, borides and carbides can be extremely hard materials.
- **Option C: They retain metallic conductivity.**
- Many interstitial compounds do retain some metallic properties, including conductivity, although this can vary based on the specific compound.
- **Option D: Their chemical reactivity is very high.**
- Interstitial compounds are generally more chemically inert than their parent metals. They do not react as readily as pure metals, which means their chemical reactivity is not high.

3. **Conclusion**:
Based on the analysis, the statement that is not a property of interstitial compounds is **Option D: Their chemical reactivity is very high**. Interstitial compounds are typically more stable and less reactive than their parent metals.

### Final Answer:
**Option D: Their chemical reactivity is very high.**

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