Which of the following is not a perfect tetrahedral species?

Options

A. `"CCl"_(4)`
B. `NH_(4)^(+)`
C. `POCl_(3)`
D. `SiF_(4)`

Explanation

To determine which of the following species is not a perfect tetrahedral species, we need to analyze the hybridization and molecular geometry of each compound given in the options. A perfect tetrahedral species has an sp³ hybridization and bond angles of approximately 109.5 degrees.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds we need to analyze are CCl₄, NH₄⁺, POCl₃, and SiF₄.

2. **Analyze CCl₄**:
- Central Atom: Carbon (C)
- Valence Electrons: 4 (from C) + 4 (from 4 Cl) = 8
- Hybridization Calculation:
\[ n = \frac{1}{2} \times (4 + 4) = \frac{8}{2} = 4 \]
- Hybridization: sp³
- Geometry: Tetrahedral
- Conclusion: CCl₄ is a perfect tetrahedral species.

3. **Analyze NH₄⁺**:
- Central Atom: Nitrogen (N)
- Valence Electrons: 5 (from N) + 4 (from 4 H) - 1 (due to +1 charge) = 8
- Hybridization Calculation:
\[ n = \frac{1}{2} \times (5 + 4 - 1) = \frac{8}{2} = 4 \]
- Hybridization: sp³
- Geometry: Tetrahedral
- Conclusion: NH₄⁺ is a perfect tetrahedral species.

4. **Analyze POCl₃**:
- Central Atom: Phosphorus (P)
- Valence Electrons: 5 (from P) + 3 (from 3 Cl) + 2 (from O) = 10
- Hybridization Calculation:
\[ n = \frac{1}{2} \times (5 + 3 + 2) = \frac{10}{2} = 5 \]
- Hybridization: sp³d (not sp³)
- Geometry: Trigonal bipyramidal with distortion (due to lone pairs)
- Conclusion: POCl₃ is not a perfect tetrahedral species.

5. **Analyze SiF₄**:
- Central Atom: Silicon (Si)
- Valence Electrons: 4 (from Si) + 4 (from 4 F) = 8
- Hybridization Calculation:
\[ n = \frac{1}{2} \times (4 + 4) = \frac{8}{2} = 4 \]
- Hybridization: sp³
- Geometry: Tetrahedral
- Conclusion: SiF₄ is a perfect tetrahedral species.

### Final Answer:
The species that is **not a perfect tetrahedral species** is **POCl₃**.

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