Which compound/s is/are covalent hydrides?

Options

A. `CH_(4)`
B. `CsH`
C. `HCl`
D. `NaH`

Answer

To determine which compounds are covalent hydrides, we need to analyze the nature of the bonds formed between hydrogen and the other elements in the given compounds. Covalent hydrides are formed when there is a small difference in electronegativity between hydrogen and the other element, leading to the formation of covalent bonds.

### Step-by-Step Solution:

1. **Identify the Compounds**:
The compounds we need to analyze are CH₄ (methane), CsH (cesium hydride), HCl (hydrochloric acid), and NaH (sodium hydride).

2. **Analyze CH₄ (Methane)**:
- Carbon (C) has an electronegativity of 2.5.
- Hydrogen (H) has an electronegativity of 2.1.
- The difference in electronegativity = |2.5 - 2.1| = 0.4.
- Since the difference is small, CH₄ forms a covalent bond and is a covalent hydride.

3. **Analyze CsH (Cesium Hydride)**:
- Cesium (Cs) is an alkali metal with a very low electronegativity (approximately 0.7).
- The difference in electronegativity = |0.7 - 2.1| = 1.4.
- This large difference indicates that CsH forms an ionic bond, making it an ionic hydride, not a covalent hydride.

4. **Analyze HCl (Hydrochloric Acid)**:
- Chlorine (Cl) has an electronegativity of 3.0.
- The difference in electronegativity = |3.0 - 2.1| = 0.9.
- This difference is relatively small, so HCl forms a covalent bond and is a covalent hydride.

5. **Analyze NaH (Sodium Hydride)**:
- Sodium (Na) is also an alkali metal with an electronegativity of approximately 0.9.
- The difference in electronegativity = |0.9 - 2.1| = 1.2.
- This large difference indicates that NaH forms an ionic bond, making it an ionic hydride.

### Conclusion:
The compounds that are covalent hydrides are:
- **CH₄ (Methane)**
- **HCl (Hydrochloric Acid)**

### Final Answer:
**Option 1 (CH₄) and Option 3 (HCl) are covalent hydrides.**

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