The coordination numbers of Co in `[Co(Cl)(en)_(2)]Cl` is_________________.
(en=ethane-1,2-diamine)

Explanation

To determine the coordination number of cobalt in the complex \([Co(Cl)(en)_2]Cl\), we can follow these steps:

### Step 1: Identify the Ligands
In the given complex, we have:
- One chloride ion (Cl⁻) which is a monodentate ligand (it can donate one pair of electrons).
- Two ethane-1,2-diamine (en) ligands, which are bidentate ligands (each can donate two pairs of electrons).

### Step 2: Count the Donor Atoms
- Each bidentate ligand (en) can coordinate through two donor atoms (the two nitrogen atoms in the amine groups).
- Therefore, for two bidentate ligands, the total number of donor atoms contributed is:
\[ 2 \text{ (from first en)} + 2 \text{ (from second en)} = 4 \]
- The chloride ion contributes 1 donor atom.

### Step 3: Calculate the Total Coordination Number
Now, we add the contributions from both types of ligands:
\[ \text{Total coordination number} = 4 \text{ (from en)} + 1 \text{ (from Cl)} = 5 \]

### Conclusion
Thus, the coordination number of cobalt in the complex \([Co(Cl)(en)_2]Cl\) is **5**.

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