Which of the following has square planar structure

Options

A. `[NiCI_(4))]^(2-)`
B. `[Ni(CO)_(4)]`
C. `[Ni(CN)_(4)]^(2-)`
D. None of the above

Explanation

To determine which of the given compounds has a square planar structure, we need to analyze the hybridization of the central metal atom in each compound. The square planar geometry is typically associated with dsp² hybridization. Let's go through the compounds step by step.

### Step 1: Identify the Compounds
The compounds we need to analyze are:
1. NiCl₄²⁻
2. Ni(CO)₄
3. Ni(CN)₄²⁻

### Step 2: Analyze NiCl₄²⁻
1. **Calculate the Oxidation State of Nickel:**
- Chlorine (Cl) is a -1 ligand, and there are 4 Cl atoms.
- Let the oxidation state of Ni be x.
- The equation is: x + 4(-1) = -2
- Solving gives: x - 4 = -2 → x = +2

2. **Determine the Electron Configuration:**
- Nickel (Ni) has an atomic number of 28, so its electron configuration is [Ar] 3d⁸ 4s².
- In the +2 oxidation state, it becomes 3d⁸ 4s⁰.

3. **Hybridization:**
- With 4 Cl⁻ ligands (weak field), the hybridization is sp³.
- Therefore, NiCl₄²⁻ has a tetrahedral structure, not square planar.

### Step 3: Analyze Ni(CO)₄
1. **Calculate the Oxidation State of Nickel:**
- CO is a neutral ligand, so the oxidation state of Ni remains 0.

2. **Determine the Electron Configuration:**
- Ni in its neutral state is 3d⁸ 4s².

3. **Hybridization:**
- CO is a strong field ligand, causing pairing of electrons.
- The configuration becomes 3d¹⁰ 4s⁰.
- The hybridization is sp³, leading to a tetrahedral structure.

### Step 4: Analyze Ni(CN)₄²⁻
1. **Calculate the Oxidation State of Nickel:**
- CN⁻ is a -1 ligand, and there are 4 CN⁻ ligands.
- Let the oxidation state of Ni be x.
- The equation is: x + 4(-1) = -2
- Solving gives: x - 4 = -2 → x = +2

2. **Determine the Electron Configuration:**
- In the +2 oxidation state, Ni is 3d⁸ 4s⁰.

3. **Hybridization:**
- CN⁻ is a strong field ligand, promoting pairing of electrons.
- The configuration becomes 3d¹⁰ 4s⁰.
- The hybridization is dsp², which corresponds to a square planar structure.

### Conclusion
Among the compounds analyzed, **Ni(CN)₄²⁻** has a square planar structure due to its dsp² hybridization.

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