The sum of coordination number and oxidation number of the metal M in the complex `[M(en)_(2) (C_(2)O_(4))]Cl` (where en is ethylenediamine) is:

Options

A. 9
B. 6
C. 7
D. 8

Explanation

To find the sum of the coordination number and the oxidation number of the metal M in the complex \([M(en)_{2}(C_{2}O_{4})]Cl\), we will follow these steps:

### Step 1: Determine the Oxidation Number of Metal M

1. **Identify the charge of the complex**: The complex \([M(en)_{2}(C_{2}O_{4})]Cl\) has a chloride ion (Cl) outside the coordination sphere, which has a charge of -1. Therefore, the overall charge of the complex cation must be +1.

2. **Identify the charges of the ligands**:
- Ethylenediamine (en) is a neutral ligand, contributing 0 to the charge.
- The oxalate ion \((C_{2}O_{4})^{2-}\) has a charge of -2.

3. **Set up the equation**:
Let the oxidation state of M be \(x\). The equation for the charge balance will be:
\[ x + 0 - 2 = +1 \]
Simplifying this gives:
\[ x - 2 = 1 \implies x = 3 \]
Therefore, the oxidation number of M is +3.

### Step 2: Determine the Coordination Number of Metal M

1. **Identify the donor atoms**:
- Ethylenediamine (en) is a bidentate ligand, meaning it has 2 donor atoms. Since there are 2 en ligands, they contribute:
\[ 2 \times 2 = 4 \text{ donor atoms} \]
- The oxalate ion \((C_{2}O_{4})^{2-}\) is also a bidentate ligand, contributing 2 donor atoms.

2. **Calculate the total coordination number**:
The total coordination number is the sum of the donor atoms from both types of ligands:
\[ 4 \text{ (from en)} + 2 \text{ (from } C_{2}O_{4}) = 6 \]
Therefore, the coordination number of M is 6.

### Step 3: Calculate the Sum of Coordination Number and Oxidation Number

Now, we add the oxidation number and the coordination number:
\[ \text{Sum} = \text{Oxidation Number} + \text{Coordination Number} = 3 + 6 = 9 \]

### Final Answer
The sum of the coordination number and oxidation number of the metal M in the complex \([M(en)_{2}(C_{2}O_{4})]Cl\) is **9**.

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