Which of following has square planar shape ?

Options

A. `XeF_4`
B. `SiCl_4`
C. `NH_4^(+)`
D. `BF_4^(-)`

Answer

To determine which of the given molecules has a square planar shape, we will analyze each option step by step.

### Step 1: Analyze the first option - XeF4
1. **Identify the central atom**: The central atom in XeF4 is Xenon (Xe).
2. **Count valence electrons**: Xenon has 8 valence electrons. Each fluorine (F) contributes 1 electron, and there are 4 fluorine atoms, contributing a total of 4 electrons.
3. **Draw the Lewis structure**: Connect the 4 fluorine atoms to the xenon atom with single bonds. This uses 4 of the 8 valence electrons, leaving 4 electrons.
4. **Determine lone pairs**: The remaining 4 electrons will form 2 lone pairs on the xenon atom.
5. **Calculate the steric number**: The steric number is calculated as the number of sigma bonds plus the number of lone pairs. Here, there are 4 sigma bonds and 2 lone pairs:
\[ \text{Steric number} = 4 + 2 = 6 \]
6. **Determine hybridization**: A steric number of 6 corresponds to sp³d² hybridization.
7. **Predict geometry**: The geometry for sp³d² hybridization is octahedral.
8. **Determine shape**: In an octahedral geometry with 2 lone pairs, the shape is square planar, as the lone pairs occupy opposite positions.

### Conclusion for XeF4
- **Shape**: Square planar

### Step 2: Analyze the second option - SiCl4
1. **Identify the central atom**: The central atom is Silicon (Si).
2. **Count valence electrons**: Silicon has 4 valence electrons, and each chlorine contributes 1 electron, totaling 4 from 4 chlorines.
3. **Draw the Lewis structure**: Connect the 4 chlorine atoms to silicon with single bonds. All 4 valence electrons are used.
4. **Determine lone pairs**: There are no lone pairs on silicon.
5. **Calculate the steric number**:
\[ \text{Steric number} = 4 + 0 = 4 \]
6. **Determine hybridization**: A steric number of 4 corresponds to sp³ hybridization.
7. **Predict geometry**: The geometry for sp³ hybridization is tetrahedral.
8. **Determine shape**: The shape is also tetrahedral, as there are no lone pairs.

### Conclusion for SiCl4
- **Shape**: Tetrahedral

### Step 3: Analyze the third option - NH4+
1. **Identify the central atom**: The central atom is Nitrogen (N).
2. **Count valence electrons**: Nitrogen has 5 valence electrons. There are 4 hydrogens contributing 4 electrons.
3. **Draw the Lewis structure**: Connect the 4 hydrogens to nitrogen with single bonds. The nitrogen uses all 5 electrons.
4. **Determine lone pairs**: There are no lone pairs on nitrogen.
5. **Calculate the steric number**:
\[ \text{Steric number} = 4 + 0 = 4 \]
6. **Determine hybridization**: A steric number of 4 corresponds to sp³ hybridization.
7. **Predict geometry**: The geometry for sp³ hybridization is tetrahedral.
8. **Determine shape**: The shape is also tetrahedral, as there are no lone pairs.

### Conclusion for NH4+
- **Shape**: Tetrahedral

### Step 4: Analyze the fourth option - BF4-
1. **Identify the central atom**: The central atom is Boron (B).
2. **Count valence electrons**: Boron has 3 valence electrons. Each fluorine contributes 1 electron, totaling 4 from 4 fluorines. The negative charge indicates an additional electron.
3. **Draw the Lewis structure**: Connect the 4 fluorines to boron with single bonds. Boron uses all 3 electrons and gains 1 from the negative charge.
4. **Determine lone pairs**: There are no lone pairs on boron.
5. **Calculate the steric number**:
\[ \text{Steric number} = 4 + 0 = 4 \]
6. **Determine hybridization**: A steric number of 4 corresponds to sp³ hybridization.
7. **Predict geometry**: The geometry for sp³ hybridization is tetrahedral.
8. **Determine shape**: The shape is also tetrahedral, as there are no lone pairs.

### Conclusion for BF4-
- **Shape**: Tetrahedral

### Final Answer
The only molecule that has a square planar shape is **XeF4**.