Which of the following complexes has a geometry different from others ?

Options

A. `[NiCl_(4)]^(2-)`
B. `Ni(CO)_(4)`
C. `[Ni(CN)_(4)]^(2-)`
D. `[Zn(NH_(3))_(4)]^(2+)`

Answer

To determine which of the following complexes has a geometry different from the others, we will analyze the geometry of each complex based on their oxidation states, electronic configurations, and hybridization.

### Step-by-Step Solution:

1. **Identify the complexes:**
- NiCl4^2-
- Ni(CO)4
- Ni(CN)4^2-
- Zn(NH3)4^2+

2. **Calculate the oxidation states:**
- For NiCl4^2-:
- Let the oxidation state of Ni be x.
- The equation becomes: x + (-1) * 4 = -2
- Therefore, x = +2. (Ni is in +2 oxidation state)

- For Ni(CO)4:
- CO is a neutral ligand, so the oxidation state of Ni is 0.

- For Ni(CN)4^2-:
- Let the oxidation state of Ni be x.
- The equation becomes: x + (-1) * 4 = -2
- Therefore, x = +2. (Ni is in +2 oxidation state)

- For Zn(NH3)4^2+:
- NH3 is a neutral ligand, so the oxidation state of Zn is +2.

3. **Determine the electronic configurations:**
- For NiCl4^2- (Ni in +2 state):
- Ground state configuration: [Ar] 3d^8 4s^2 → 3d^8
- For Ni(CO)4 (Ni in 0 state):
- Configuration remains: [Ar] 3d^8 4s^2 → 3d^8 4s^2
- For Ni(CN)4^2- (Ni in +2 state):
- Configuration: [Ar] 3d^8 → 3d^8
- For Zn(NH3)4^2+ (Zn in +2 state):
- Configuration: [Ar] 3d^10 → 3d^10

4. **Analyze the ligand field strength:**
- Cl^- is a weak field ligand (high spin).
- CO is a strong field ligand (low spin).
- CN^- is a strong field ligand (low spin).
- NH3 is a strong field ligand (low spin).

5. **Determine hybridization and geometry:**
- For NiCl4^2-:
- Hybridization: sp^3 (due to 4 ligands and weak field → high spin)
- Geometry: Tetrahedral.

- For Ni(CO)4:
- Hybridization: sp^3 (neutral ligand)
- Geometry: Tetrahedral.

- For Ni(CN)4^2-:
- Hybridization: dsp^2 (strong field → low spin)
- Geometry: Square planar.

- For Zn(NH3)4^2+:
- Hybridization: sp^3 (neutral ligand)
- Geometry: Tetrahedral.

6. **Conclusion:**
- The geometries of the complexes are:
- NiCl4^2-: Tetrahedral
- Ni(CO)4: Tetrahedral
- Ni(CN)4^2-: Square planar
- Zn(NH3)4^2+: Tetrahedral
- The complex with a geometry different from the others is **Ni(CN)4^2-**, which has a square planar geometry.

### Final Answer:
The complex that has a geometry different from the others is **Ni(CN)4^2-** (square planar).