The value of n in the carbonyl is
`(CO)_(n)-Co-Co(CO)_(n)`

Options

A. 4
B. 5
C. 6
D. 8

Explanation

To find the value of \( n \) in the carbonyl compound represented as \( (CO)_{n}-Co-Co(CO)_{n} \), we can follow these steps:

### Step 1: Understanding the Structure
The compound can be interpreted as having two cobalt (Co) atoms connected by a bridging carbonyl (CO) group. Each cobalt atom is also bonded to \( n \) carbonyl groups.

### Step 2: Analyzing the Carbonyl Groups
In the structure \( (CO)_{n}-Co-Co(CO)_{n} \), we have:
- One cobalt atom on the left connected to \( n \) carbonyl groups.
- One cobalt atom on the right also connected to \( n \) carbonyl groups.

### Step 3: Applying the Effective Atomic Number (EAN) Rule
The effective atomic number (EAN) rule states that the stability of a metal complex can be predicted by calculating the total number of electrons around the metal center.
- The atomic number of cobalt (Co) is 27.
- Each carbonyl (CO) contributes 2 electrons.

### Step 4: Calculating the Total Electron Count
For one cobalt atom:
- The contribution from \( n \) carbonyl groups is \( 2n \) electrons.
- There is also 1 electron from the Co-Co bond.

Thus, the total electron count for one cobalt atom can be expressed as:
\[ \text{Total electrons} = 27 + 2n + 1 \]
This should equal 36 (the stable electron count for cobalt).

### Step 5: Setting Up the Equation
Setting the equation based on the EAN rule:
\[ 27 + 2n + 1 = 36 \]

### Step 6: Solving for \( n \)
Now, simplify the equation:
\[ 28 + 2n = 36 \]
Subtract 28 from both sides:
\[ 2n = 8 \]
Divide by 2:
\[ n = 4 \]

### Conclusion
Thus, the value of \( n \) in the carbonyl compound \( (CO)_{n}-Co-Co(CO)_{n} \) is **4**.

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