The coordination number and oxidation number of `Cr` in `K_(3)[Cr(C_(2)O_(4))_(3)]` are, respectively,

Options

A. `4 and +2`
B. `6 and +3`
C. `3` and `-3`
D. `3` and `0`

Explanation

To determine the coordination number and oxidation number of chromium (Cr) in the complex \( K_3[Cr(C_2O_4)_3] \), we can follow these steps:

### Step 1: Identify the Ligand
The ligand in the complex is oxalate, represented as \( C_2O_4^{2-} \). It is important to note that oxalate is a bidentate ligand, meaning it can form two bonds with the central metal ion (in this case, chromium).

### Step 2: Determine the Coordination Number
Since each oxalate ligand can bind to the chromium ion at two sites and there are three oxalate ligands in the complex, we can calculate the coordination number as follows:
- Number of oxalate ligands = 3
- Each oxalate ligand binds at 2 sites.

Thus, the coordination number of Cr is:
\[ \text{Coordination Number} = 3 \text{ (ligands)} \times 2 \text{ (bonds per ligand)} = 6 \]

### Step 3: Calculate the Oxidation Number
Next, we need to find the oxidation number of chromium (Cr) in the complex. The overall charge of the complex ion \( [Cr(C_2O_4)_3]^{3-} \) must balance with the charges from the potassium ions.

1. The charge of each potassium ion \( K^+ \) is +1. Since there are 3 potassium ions, their total contribution is:
\[ 3 \times (+1) = +3 \]

2. The charge of the oxalate ion \( C_2O_4^{2-} \) is -2. Since there are 3 oxalate ions, their total contribution is:
\[ 3 \times (-2) = -6 \]

3. Let the oxidation number of chromium be \( x \). The overall charge of the complex ion must equal the sum of the charges:
\[ x + (-6) = -3 \]

4. Solving for \( x \):
\[ x - 6 = -3 \\ x = -3 + 6 \\ x = +3 \]

### Final Answer
Thus, the coordination number of Cr is 6, and the oxidation number of Cr is +3.

### Summary
- **Coordination Number of Cr**: 6
- **Oxidation Number of Cr**: +3