Assertion (A): Alkali metals can form ionic hydrides which contain hydride ion, H.
Reason (R ): The alkali metals have low EN. Their hydrides conduct electricity, when fused and liberate hydrogen at the anode.

Options

A. If both (A) and (R ) are correct and (R ) is the correct explanation of (A).
B. If both (A) and (R ) are correct, but (R ) is not the correct explanation of (A).
C. If (A) is correct, but (R ) is incorrect.
D. If (A) is incorrect, but (R ) is correct.

Answer

To analyze the question regarding the assertion and reason related to alkali metals and their hydrides, we can break down the solution into clear steps:

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that alkali metals can form ionic hydrides which contain the hydride ion (H⁻).
- Alkali metals (like lithium, sodium, potassium, etc.) react with hydrogen to form hydrides. For example, sodium reacts with hydrogen to form sodium hydride (NaH), which contains the hydride ion (H⁻).

2. **Understanding the Reason (R)**:
- The reason provided states that alkali metals have low electronegativity (EN) and that their hydrides can conduct electricity when fused, liberating hydrogen at the anode.
- Alkali metals have low electronegativity because they are located on the left side of the periodic table. This means they readily lose their outermost electron to form positive ions, which is essential for the formation of ionic compounds.

3. **Conductivity of Hydrides**:
- When alkali metal hydrides are melted (fused), they dissociate into ions. For example, NaH will dissociate into Na⁺ and H⁻ ions.
- In the molten state, these ions are free to move, allowing the hydride to conduct electricity.

4. **Electrolysis of Hydrides**:
- During electrolysis, at the anode, the hydride ion (H⁻) loses an electron (oxidation) to form hydrogen gas (H₂).
- The overall reaction at the anode can be represented as:
\[ 2H⁻ \rightarrow H₂ + 2e⁻ \]
- At the cathode, the metal cation (e.g., Na⁺) gains electrons to form solid metal.

5. **Conclusion**:
- Both the assertion and the reason are correct. The reason correctly explains why alkali metals can form ionic hydrides and why these hydrides conduct electricity when fused.

### Final Answer:
- The correct choice is **Option A**: Both Assertion and Reason are correct, and Reason is the correct explanation of Assertion.

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