The complex ion `[Cu(NH_3)_4]^(2+)` is

Options

A. tetrahedral
B. square planar
C. Both (a) and (b)
D. None of these

Explanation

To determine the geometry of the complex ion \([Cu(NH_3)_4]^{2+}\), we can follow these steps:

### Step 1: Identify the oxidation state of copper in the complex.
The complex ion \([Cu(NH_3)_4]^{2+}\) has an overall charge of +2. Since ammonia (NH₃) is a neutral ligand, the oxidation state of copper (Cu) in this complex must be +2.

### Step 2: Determine the electronic configuration of Cu²⁺.
Copper (Cu) has an atomic number of 29, which means its electronic configuration in the neutral state is:
\[ \text{Cu: } [Ar] 3d^{10} 4s^1 \]
When copper loses two electrons to form Cu²⁺, it loses the 4s electron and one of the 3d electrons:
\[ \text{Cu}^{2+}: [Ar] 3d^9 \]

### Step 3: Analyze the coordination number.
In the complex \([Cu(NH_3)_4]^{2+}\), there are four ammonia ligands coordinated to the copper ion. The coordination number is 4.

### Step 4: Determine the geometry based on the coordination number.
For a coordination number of 4, the possible geometries are:
- Tetrahedral
- Square planar

### Step 5: Consider the electronic configuration and ligand field theory.
In the case of Cu²⁺ with a \(3d^9\) configuration, the presence of strong field ligands like NH₃ can lead to a square planar geometry due to the stabilization of the \(d_{x^2-y^2}\) orbital. This is a common behavior for \(d^8\) metal ions, but Cu²⁺ with \(d^9\) can also exhibit square planar geometry due to the strong field nature of NH₃.

### Conclusion:
The complex ion \([Cu(NH_3)_4]^{2+}\) is square planar.

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