Consider `LiH, MgH_2` and `CuH`:

Options

A. all are ionic hydrides
B. `LiH,MgH_(2)` are ionic, whereas `CUH` is covalent
C. all are covalent
D. `LiH` is ionic, `MgH_(2)` is covalent `CuH` is metqallic

Answer

To determine the nature of the hydrides LiH (lithium hydride), MgH₂ (magnesium hydride), and CuH (copper hydride), we can analyze each compound based on the properties of the elements involved.

### Step-by-Step Solution:

1. **Identify the Type of Elements**:
- Lithium (Li) is an alkali metal.
- Magnesium (Mg) is an alkaline earth metal.
- Copper (Cu) is a transition metal.

2. **Analyze Lithium Hydride (LiH)**:
- Lithium donates one electron to hydrogen.
- The bond formed between lithium and hydrogen is primarily ionic due to the significant difference in electronegativity between lithium and hydrogen.
- **Conclusion**: LiH is an ionic hydride.

3. **Analyze Magnesium Hydride (MgH₂)**:
- Magnesium has two valence electrons and can share these electrons with hydrogen atoms.
- The bond formed is more covalent in nature because magnesium shares its electrons with hydrogen rather than completely transferring them.
- **Conclusion**: MgH₂ is a covalent hydride.

4. **Analyze Copper Hydride (CuH)**:
- Copper can exhibit metallic bonding characteristics.
- In CuH, the bonding involves sharing of electrons, which is typical of metallic hydrides.
- **Conclusion**: CuH is a metallic hydride.

5. **Summarize the Findings**:
- LiH: Ionic hydride
- MgH₂: Covalent hydride
- CuH: Metallic hydride

6. **Evaluate the Options**:
- Option 1: All are ionic hydrides (Incorrect)
- Option 2: LiH and MgH₂ are ionic, CuH is covalent (Incorrect)
- Option 3: All are covalent (Incorrect)
- Option 4: LiH is ionic, MgH₂ is covalent, CuH is metallic (Correct)

### Final Answer:
The correct classification is:
- Lithium hydride (LiH) is ionic,
- Magnesium hydride (MgH₂) is covalent,
- Copper hydride (CuH) is metallic.