`[Co(e n)_(3)]^(3+)` ion is expected to show :-

Options

A. Two optically active isomers
B. Two optically inactive isomers
C. four optically active isomers, cis, d & `l` from and trans d & `l` form
D. None

Answer

To determine the expected behavior of the `[Co(en)₃]^(3+)` ion, we need to analyze its structure and properties step by step.

### Step 1: Identify the Coordination Complex
The complex in question is `[Co(en)₃]^(3+)`, where "en" stands for ethylenediamine, a bidentate ligand. This means that each ethylenediamine molecule can bind to the cobalt ion at two sites.

**Hint:** Remember that bidentate ligands can create chelate rings with the metal ion.

### Step 2: Determine the Coordination Number
Cobalt in this complex has a coordination number of 6 because it is surrounded by three ethylenediamine ligands, each contributing two coordination sites.

**Hint:** The coordination number is determined by the number of donor atoms from ligands surrounding the metal ion.

### Step 3: Analyze the Geometry
With a coordination number of 6, the geometry of the complex is octahedral. In an octahedral arrangement, the ligands can be arranged in various ways, leading to different isomers.

**Hint:** Visualize the octahedral structure to understand how the ligands can be positioned relative to each other.

### Step 4: Consider Optical Isomerism
In octahedral complexes with bidentate ligands, the arrangement of the ligands can lead to the formation of optical isomers. Optical isomers are non-superimposable mirror images of each other. For `[Co(en)₃]^(3+)`, there are two distinct arrangements that can exist, leading to two optically active isomers.

**Hint:** Think about how the arrangement of ligands can create chiral centers, resulting in non-superimposable mirror images.

### Step 5: Conclusion
Thus, the `[Co(en)₃]^(3+)` ion is expected to show two optically active isomers due to its chiral nature in the octahedral geometry.

**Final Answer:** The correct answer is that `[Co(en)₃]^(3+)` shows two optically active isomers.