Examples of polymeric hydrides are

Options

A. `BH_(3)`
B. `BeH_(2)`
C. `NaH`
D. `CaH_(2)`

Answer

To solve the question about examples of polymeric hydrides, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Hydrides**:
- Hydrides are chemical compounds in which hydrogen is combined with another element. In these compounds, hydrogen typically exists as a hydride ion (H⁻).

2. **Classify Types of Hydrides**:
- Hydrides can be classified into three main types based on the nature of the bonding:
- **Saline (Ionic) Hydrides**: Formed with alkali and alkaline earth metals.
- **Metallic Hydrides**: Formed with transition metals.
- **Covalent Hydrides**: Formed with nonmetals.
- Additionally, there is a fourth category known as **Polymeric (or Dimeric) Hydrides**.

3. **Identify Polymeric Hydrides**:
- Polymeric hydrides are characterized by their structure, where they consist of repeating units of hydride ions and other elements. They often have complex structures and can exist in solid, liquid, or gaseous forms.

4. **Evaluate the Given Options**:
- The options provided are:
- **BH₃**: Boron hydride, which is not a polymeric hydride.
- **BeH₂**: Beryllium hydride, which is a known example of a polymeric hydride.
- **NaH**: Sodium hydride, which is an ionic hydride.
- **CaH₂**: Calcium hydride, which is also an ionic hydride.

5. **Select the Correct Answer**:
- Among the options, **BeH₂ (Beryllium Hydride)** is the only polymeric hydride. Therefore, the answer to the question is **BeH₂**.

### Final Answer:
The example of a polymeric hydride is **BeH₂ (Beryllium Hydride)**.

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