Co-ordination number of central atom in `Na_(3)[Al(C_(2)O_(4))_(3)]` and `[Co(en)_(2)Cl]Cl` are:

Options

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

Answer

To find the coordination number of the central atom in the complexes `Na3[Al(C2O4)3]` and `[Co(en)2Cl]Cl`, we will analyze each complex step by step.

### Step 1: Analyze the first complex `Na3[Al(C2O4)3]`

1. **Identify the central atom**: In this complex, the central atom is Aluminum (Al).
2. **Identify the ligands**: The ligands attached to Aluminum are oxalate ions (C2O4) which are bidentate ligands.
3. **Determine the number of ligands**: There are 3 oxalate ligands in the complex.
4. **Calculate the coordination number**: Since each oxalate ion can donate 2 pairs of electrons (due to being bidentate), the total coordination number contributed by the ligands is:
\[ \text{Coordination number} = \text{Number of ligands} \times \text{Number of donation sites per ligand} = 3 \times 2 = 6 \]

### Step 2: Analyze the second complex `[Co(en)2Cl]Cl`

1. **Identify the central atom**: In this complex, the central atom is Cobalt (Co).
2. **Identify the ligands**: The ligands attached to Cobalt are ethylenediamine (en) and chloride (Cl).
3. **Determine the number of ligands**: There are 2 ethylenediamine ligands and 1 chloride ligand.
4. **Calculate the coordination number**:
- Ethylenediamine (en) is also a bidentate ligand, so each can donate 2 pairs of electrons.
- Chloride (Cl) is a unidentate ligand, donating 1 pair of electrons.
- Therefore, the total coordination number is:
\[ \text{Coordination number} = (2 \text{ en} \times 2) + (1 \text{ Cl} \times 1) = 4 + 1 = 5 \]

### Final Answer
- The coordination number of the central atom in `Na3[Al(C2O4)3]` is **6**.
- The coordination number of the central atom in `[Co(en)2Cl]Cl` is **5**.