Which molecule is planar?

Options

A. `SF_(4)`
B. `XeF_(4)`
C. `NF_(3)`
D. `SiF_(4)`

Answer

To determine which molecule is planar among the given options, we will analyze the molecular geometry and hybridization of each molecule. Here’s a step-by-step solution:

### Step 1: Identify the Molecules
Let's assume the options provided are:
1. SF4 (Sulfur Tetrafluoride)
2. XeF4 (Xenon Tetrafluoride)
3. NF3 (Nitrogen Trifluoride)
4. SiF4 (Silicon Tetrafluoride)

### Step 2: Determine the Valence Electrons
- **SF4**: Sulfur has 6 valence electrons. With 4 fluorine atoms (each contributing 1 electron), the total is 6 + 4 = 10 electrons.
- **XeF4**: Xenon has 8 valence electrons. With 4 fluorine atoms, the total is 8 + 4 = 12 electrons.
- **NF3**: Nitrogen has 5 valence electrons. With 3 fluorine atoms, the total is 5 + 3 = 8 electrons.
- **SiF4**: Silicon has 4 valence electrons. With 4 fluorine atoms, the total is 4 + 4 = 8 electrons.

### Step 3: Calculate the Steric Number
The steric number is calculated using the formula:
\[ \text{Steric Number} = \text{Number of Sigma Bonds} + \text{Number of Lone Pairs} \]

- **SF4**: 4 sigma bonds + 1 lone pair = 5 (Trigonal bipyramidal geometry, but the shape is see-saw, which is not planar).
- **XeF4**: 4 sigma bonds + 2 lone pairs = 6 (Octahedral geometry, but the shape is square planar, which is planar).
- **NF3**: 3 sigma bonds + 1 lone pair = 4 (Tetrahedral geometry, which is not planar).
- **SiF4**: 4 sigma bonds + 0 lone pairs = 4 (Tetrahedral geometry, which is not planar).

### Step 4: Analyze the Geometry and Shape
- **SF4**: The presence of a lone pair makes it a see-saw shape, which is not planar.
- **XeF4**: The shape is square planar due to the arrangement of the fluorine atoms in one plane with the lone pairs above and below, making it planar.
- **NF3**: The molecule has a tetrahedral shape, which is not planar.
- **SiF4**: The tetrahedral shape is also not planar.

### Conclusion
The only molecule that is planar among the options is **XeF4** (Xenon Tetrafluoride).

### Final Answer
**XeF4 is the planar molecule.**

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