Assertion : `H_2N - NH_2` is a chelating ligand.
Reason : A chelating ligand must possess two or more lone pairs at such a distance that it may form suitable strain free rings at the metal ion.

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If assertion is false but reason is true.

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Understanding the Assertion
The assertion states that `H2N - NH2` (hydrazine) is a chelating ligand. A chelating ligand is a molecule that can form multiple bonds to a metal ion, effectively "grabbing" the metal ion and forming a stable complex.

### Step 2: Analyzing the Structure of Hydrazine
Hydrazine has the formula `H2N - NH2`, which means it contains two nitrogen atoms, each with a lone pair of electrons. The presence of these lone pairs is crucial for the formation of coordinate bonds with a metal ion.

### Step 3: Understanding the Reason
The reason states that a chelating ligand must possess two or more lone pairs at such a distance that it may form suitable strain-free rings at the metal ion. This is true because for a ligand to be classified as chelating, it should be able to bind to a metal ion at multiple sites, ideally forming a stable ring structure.

### Step 4: Evaluating the Assertion and Reason
- **Assertion**: Hydrazine can act as a chelating ligand because it has two nitrogen atoms, each with a lone pair, allowing it to bind to a metal ion.
- **Reason**: The reason correctly describes the characteristics of a chelating ligand, emphasizing the importance of having multiple lone pairs and the ability to form stable, strain-free rings.

### Conclusion
Both the assertion and the reason are true. The assertion is correct because hydrazine can act as a chelating ligand, and the reason is also true as it accurately describes the requirements for a ligand to be considered chelating.

### Final Answer
- **Assertion**: True
- **Reason**: True
- **Conclusion**: Both the assertion and reason are true, and the reason correctly explains the assertion.

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