The oxidation number of cobalt in `K[Co(CO)_(4)]` is:

Options

A. `+1`
B. `+3`
C. `-1`
D. `-3`

Explanation

To find the oxidation number of cobalt in the complex compound \( K[Co(CO)_{4}] \), we can follow these steps:

### Step 1: Identify the components of the complex
The complex \( K[Co(CO)_{4}] \) consists of a potassium ion \( K^{+} \) and the complex ion \( [Co(CO)_{4}]^{-} \).

### Step 2: Determine the charge of the complex ion
Since potassium \( K^{+} \) has a charge of +1, the complex ion \( [Co(CO)_{4}] \) must have a charge of -1 to balance the overall charge of the compound.

### Step 3: Assign oxidation states
Let the oxidation state of cobalt be \( x \). Each carbonyl \( CO \) is a neutral ligand, meaning it does not contribute to the charge. Therefore, the total contribution from the four carbonyl ligands is \( 4 \times 0 = 0 \).

### Step 4: Set up the equation
The equation for the charge of the complex ion can be set up as follows:
\[ x + 0 = -1 \]
This simplifies to:
\[ x = -1 \]

### Step 5: Conclusion
Thus, the oxidation number of cobalt in \( K[Co(CO)_{4}] \) is \( -1 \).

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