Which of the following is not tetrahedral in shape ?

Options

A. `NH_(4)^(+)`
B. `SiCl_(4)`
C. `SF_(4)`
D. `SO_(4)^(2-)`

Explanation

To determine which of the following compounds is not tetrahedral in shape, we will analyze each option based on their molecular geometry and hybridization.

### Step-by-Step Solution:

1. **Identify the Compounds:**
The compounds given are:
- NH4^+ (Ammonium ion)
- SiCl4 (Silicon tetrachloride)
- SF4 (Sulfur tetrafluoride)
- SO4^2- (Sulfate ion)

2. **Analyze NH4^+:**
- **Structure:** The ammonium ion has one nitrogen atom bonded to four hydrogen atoms.
- **Hybridization:** The hybridization of NH4^+ is sp³.
- **Shape:** The molecular shape is tetrahedral.

3. **Analyze SiCl4:**
- **Structure:** Silicon tetrachloride consists of one silicon atom bonded to four chlorine atoms.
- **Hybridization:** The hybridization of SiCl4 is also sp³.
- **Shape:** The molecular shape is tetrahedral.

4. **Analyze SF4:**
- **Structure:** Sulfur tetrafluoride has one sulfur atom bonded to four fluorine atoms and has one lone pair of electrons.
- **Hybridization:** The hybridization of SF4 is sp³d.
- **Shape:** With one lone pair, the molecular shape is seesaw, which is not tetrahedral.

5. **Analyze SO4^2-:**
- **Structure:** The sulfate ion consists of one sulfur atom bonded to four oxygen atoms (with some double bonds).
- **Hybridization:** The hybridization of SO4^2- is sp³.
- **Shape:** The molecular shape is tetrahedral.

6. **Conclusion:**
Among the four options, NH4^+, SiCl4, and SO4^2- are tetrahedral in shape, while SF4 is not tetrahedral; it has a seesaw shape due to the presence of a lone pair.

### Final Answer:
The compound that is not tetrahedral in shape is **SF4**.

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