What is the co-ordination number of the metal in `[Co(en)_2Cl_2]^+`?

Options

A. (a) `4`
B. (b) `5`
C. (c) `6`
D. (d) `3`

Explanation

To determine the coordination number of the metal in the complex ion \([Co(en)_2Cl_2]^+\), follow these steps:

### Step 1: Identify the central metal atom
The central metal atom in the complex is cobalt (Co).

### Step 2: Identify the ligands
The ligands attached to the cobalt are:
- \(en\) (ethylenediamine), which is a bidentate ligand.
- \(Cl^-\) (chloride), which is a monodentate ligand.

### Step 3: Count the number of donor atoms from ligands
- Each \(en\) ligand can donate 2 pairs of electrons (2 donor atoms).
- Since there are 2 \(en\) ligands, they contribute:
\[ 2 \, \text{(from first } en\text{)} + 2 \, \text{(from second } en\text{)} = 4 \, \text{donor atoms} \]

- The \(Cl^-\) ligands contribute 1 donor atom each. Since there are 2 \(Cl^-\) ligands, they contribute:
\[ 1 \, \text{(from first } Cl\text{)} + 1 \, \text{(from second } Cl\text{)} = 2 \, \text{donor atoms} \]

### Step 4: Calculate the total coordination number
Now, add the donor atoms from both types of ligands:
\[ 4 \, \text{(from } en\text{)} + 2 \, \text{(from } Cl\text{)} = 6 \]

### Conclusion
The coordination number of the cobalt in the complex \([Co(en)_2Cl_2]^+\) is **6**.

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