Classify the following as covalent , ionic or polymer interstital hydrides :
(i) `BeH_2 (ii) CaH_2 (iii) RbH (iv) GeH_4 (iv) TiH_2`

Explanation

To classify the given hydrides as covalent, ionic, or polymeric/interstitial, we will analyze each compound based on their bonding characteristics.

### Step-by-Step Solution:

1. **Beryllium Hydride (BeH₂)**:
- Beryllium (Be) is a metal that forms bonds by sharing electrons with hydrogen atoms. In BeH₂, the structure is polymeric due to the bridging of hydrogen atoms between beryllium atoms.
- **Classification**: **Polymeric Hydride**

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