Which of the following is interstitial hydride?

Options

A. `CaH_(2)`
B. CuH
C. `PH_(3)`
D. NaH

Answer

To determine which of the given compounds is an interstitial hydride, we will analyze each option based on their classification as hydrides.

### Step-by-Step Solution:

1. **Understand the Types of Hydrides**:
- Hydrides can be classified into three main types:
- **Ionic Hydrides**: Typically formed by s-block elements (alkali and alkaline earth metals).
- **Molecular Hydrides**: Formed by p-block elements (except noble gases).
- **Metallic or Interstitial Hydrides**: Formed by d-block and f-block elements.

2. **Analyze Each Option**:
- **Option 1: Calcium Hydride (CaH₂)**:
- Calcium is an alkaline earth metal (s-block).
- Therefore, it forms an ionic hydride.

- **Option 2: Cuprous Hydride (CuH)**:
- Copper is a transition metal (d-block).
- It can form interstitial hydrides, so this is a candidate.

- **Option 3: Phosphine (PH₃)**:
- Phosphorus is a p-block element.
- Therefore, it forms a molecular hydride.

- **Option 4: Sodium Hydride (NaH)**:
- Sodium is an alkali metal (s-block).
- It forms an ionic hydride.

3. **Conclusion**:
- Among the options analyzed, **Cuprous Hydride (CuH)** is the only interstitial hydride because it is formed by a d-block element (copper).

### Final Answer:
The interstitial hydride from the given options is **Cuprous Hydride (CuH)**.

---