Assertion `(A)`: Alkali metals form ionic hydrides.
Reason `(R)` : Alkali metals lose their valence electron which is accepted by hydrogen to form hydride ion.

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.

Explanation

To solve the question regarding the assertion and reason about alkali metals and their hydrides, we will break it down step by step.

### Step 1: Understand the Assertion
The assertion states that "Alkali metals form ionic hydrides."
- **Explanation**: Alkali metals (like lithium, sodium, potassium, etc.) are known to form hydrides when they react with hydrogen. These hydrides are ionic in nature because they consist of a metal cation (from the alkali metal) and a hydride anion (H⁻).

### Step 2: Understand the Reason
The reason states that "Alkali metals lose their valence electron which is accepted by hydrogen to form hydride ion."
- **Explanation**: Alkali metals have one valence electron in their outermost shell. When they react with hydrogen, they lose this valence electron to form a positively charged ion (M⁺). The hydrogen atom accepts this electron, resulting in the formation of a hydride ion (H⁻).

### Step 3: Analyze the Relationship Between Assertion and Reason
Now we need to determine if the reason provided correctly explains the assertion.
- The reason accurately describes the process by which alkali metals form ionic hydrides. The loss of the valence electron by the alkali metal and its acceptance by hydrogen to form H⁻ is indeed the mechanism through which these ionic hydrides are formed.

### Conclusion
Since both the assertion and the reason are correct, and the reason correctly explains the assertion, the correct answer is:
- **Option A**: Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.

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