Interstitial compounds are

Options

A. non-stoichiometric and are ionic in nature
B. non-stoichiometric and are covalent in nature
C. non-stoichiometric and are neirther typically ionic nor covalent in nature
D. stoichiometric and are neither ionic nor covalent in nature.

Answer

### Step-by-Step Solution:

1. **Definition of Interstitial Compounds**:
Interstitial compounds are formed when small atoms, such as hydrogen, nitrogen, or carbon, occupy the spaces (voids) within the crystal lattice of a metal.

2. **Characteristics of Interstitial Compounds**:
- They are generally non-stoichiometric, meaning their elemental composition does not conform to simple whole-number ratios.
- They are not typically ionic or covalent in nature, which distinguishes them from other types of compounds.

3. **Formation of Interstitial Compounds**:
- The small atoms fit into the voids created by the arrangement of the metal atoms in the crystal lattice.
- Transition metals are particularly known for forming these compounds due to their closely packed structures, which have numerous voids.

4. **Example of Interstitial Compounds**:
- An example of an interstitial compound is the formation of steel, where carbon atoms occupy the interstitial sites in the iron lattice.

5. **Conclusion**:
- Therefore, interstitial compounds are characterized as non-stoichiometric compounds that do not exhibit typical ionic or covalent bonding.