A: `[Ni(CO)_(4)]` is organometallic compound.
R: CO is organic and Niis metal.

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 solve the question regarding the assertion and reason about the compound `[Ni(CO)_(4)]`, we will analyze both the assertion (A) and the reason (R) step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that `[Ni(CO)_(4)]` is an organometallic compound.
- Organometallic compounds are defined as compounds that contain a direct bond between a carbon atom of an organic group and a metal.

2. **Analyzing the Composition of `[Ni(CO)_(4)]`**:
- In `[Ni(CO)_(4)]`, nickel (Ni) is the metal, and CO (carbon monoxide) acts as a ligand.
- CO is a neutral ligand that contains a carbon atom bonded to an oxygen atom. The carbon atom in CO can form a bond with the nickel atom.

3. **Conclusion on the Assertion**:
- Since `[Ni(CO)_(4)]` contains a direct bond between the carbon atom of CO and the nickel metal, it qualifies as an organometallic compound.
- Therefore, the assertion (A) is **correct**.

4. **Understanding the Reason (R)**:
- The reason states that CO is organic and Ni is metal.
- While it is true that Ni is a metal, CO is not considered an organic compound in the traditional sense. Organic compounds are typically defined as compounds containing carbon-hydrogen (C-H) bonds.

5. **Analyzing the Validity of the Reason**:
- The reason provided does not accurately explain why `[Ni(CO)_(4)]` is an organometallic compound. The key aspect is the direct bond between the metal and the carbon atom, not the classification of CO as organic.
- Therefore, the reason (R) is **incorrect**.

6. **Final Conclusion**:
- The assertion (A) is correct, while the reason (R) is incorrect.
- The correct answer to the question is that the assertion is true, but the reason is false.

### Final Answer:
- Assertion (A) is correct: `[Ni(CO)_(4)]` is an organometallic compound.
- Reason (R) is incorrect: CO is not classified as an organic compound in this context.