In a particular isomer of `[Co(NH_(3))_(4)Cl_(2)]`, the Cl-Co-Cl angle is `90^(@)`, the isomer is known as

Options

A. Optical isomer
B. Cis-isomer
C. Position isomer
D. Linkage isomer

Explanation

To determine the isomer of the complex `[Co(NH₃)₄Cl₂]` where the Cl-Co-Cl angle is `90°`, we can follow these steps:

### Step 1: Identify the coordination geometry
The complex `[Co(NH₃)₄Cl₂]` has a cobalt ion (Co) coordinated to four ammonia (NH₃) ligands and two chloride (Cl) ligands. Cobalt typically forms octahedral complexes in this type of coordination.

**Hint:** Remember that octahedral complexes can have different spatial arrangements of ligands.

### Step 2: Understand isomerism in octahedral complexes
In octahedral complexes, ligands can be arranged in different ways leading to isomerism. The two main types of isomers in octahedral complexes with two identical ligands are:
- **Cis isomer**: The identical ligands are adjacent to each other.
- **Trans isomer**: The identical ligands are opposite each other.

**Hint:** Think about how the positions of the ligands affect the angles between them.

### Step 3: Analyze the given angle
The problem states that the Cl-Co-Cl angle is `90°`. This angle indicates that the two chloride ligands are adjacent to each other, which corresponds to the cis arrangement.

**Hint:** Visualize the octahedral structure to see how the ligands are positioned relative to each other.

### Step 4: Conclusion
Since the Cl-Co-Cl angle is `90°`, the isomer of `[Co(NH₃)₄Cl₂]` is the **cis isomer**.

**Final Answer:** The isomer is known as the **Cis isomer**.