A: `NiCI_2` is more stable than `PtCl_(2)`
R: `K_(2) PtCl_(6)` is more stable than `K_2NiCI_6`

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2)
C. If Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To analyze the assertion and reason provided in the question, we can break it down step by step.

### Step 1: Understanding the Assertion
The assertion states that NiCl₂ is more stable than PtCl₂.
- Nickel (Ni) and platinum (Pt) are both transition metals, but they exhibit different stabilities in their respective chlorides.
- Nickel typically has a stable oxidation state of +2, while platinum can exist in multiple oxidation states, including +2 and +4.
- The +2 oxidation state of nickel is generally more stable due to its electronic configuration and the lower energy of its d-orbitals compared to platinum.

### Step 2: Understanding the Reason
The reason states that K₂PtCl₆ is more stable than K₂NiCl₆.
- K₂PtCl₆ contains platinum in the +4 oxidation state, which is a common and stable oxidation state for platinum in coordination complexes.
- K₂NiCl₆ contains nickel in the +4 oxidation state, which is less stable than the +2 state.
- The stability of K₂PtCl₆ can be attributed to the ability of platinum to stabilize higher oxidation states due to its larger atomic size and the effective shielding of d-electrons.

### Step 3: Analyzing the Relationship between Assertion and Reason
- Both the assertion and the reason are correct statements regarding the stability of the respective compounds.
- The assertion highlights the stability of NiCl₂ compared to PtCl₂, while the reason discusses the stability of their respective hexachlorocomplexes.
- The stability of K₂PtCl₆ compared to K₂NiCl₆ supports the assertion, as it shows that platinum can stabilize higher oxidation states better than nickel.

### Conclusion
Both the assertion and reason are correct, and the reason correctly explains the assertion.

### Final Answer
Both A and R are correct, and R is the correct explanation for A.

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