The effective atomic number of `Co(CO)_(4)` is 35 and hence is less stable. It attains stability by

Options

A. Oxidation of Co
B. Reduction of Co
C. Dimerisation
D. Both (b) and (c)

Answer

To solve the question regarding the stability of `Co(CO)_(4)` and how it attains stability, we can break down the solution into clear steps:

### Step-by-Step Solution:

1. **Identify the Atomic Number of Cobalt**:
The atomic number of cobalt (Co) is 27.

2. **Determine the Contribution of Ligands**:
In `Co(CO)_(4)`, there are four carbonyl (CO) ligands. Each carbonyl ligand donates 2 electrons.
\[ \text{Total electrons from ligands} = 4 \text{ (CO)} \times 2 \text{ (electrons per CO)} = 8 \text{ electrons} \]

3. **Calculate the Effective Atomic Number (EAN)**:
The effective atomic number is calculated by adding the electrons from cobalt and the electrons donated by the ligands.
\[ \text{EAN} = \text{Atomic number of Co} + \text{Electrons from ligands} = 27 + 8 = 35 \]

4. **Analyze the Stability**:
An EAN of 35 indicates that the complex is less stable because it does not achieve a noble gas configuration. The stable configuration for cobalt would be 36 electrons, which corresponds to the electron configuration of krypton.

5. **Stability through Dimerization**:
To attain stability, `Co(CO)_(4)` can undergo dimerization. In this process, two `Co(CO)_(4)` molecules combine, allowing the unpaired electrons on the cobalt atoms to pair up and form a covalent bond. This results in a more stable electron configuration.

6. **Alternative Stability through Reduction**:
Another way for `Co(CO)_(4)` to attain stability is through reduction, where cobalt can accept electrons (or hydrogen) to fill its electron shell, moving towards the stable configuration of 36 electrons.

7. **Conclusion**:
Therefore, `Co(CO)_(4)` attains stability by both dimerization and reduction, leading to a more stable electronic configuration.

### Final Answer:
`Co(CO)_(4)` attains stability by dimerization and reduction.

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