Which one of the following does not have a pyramidal shape?

Options

A. `P(CH_(3))_(3)`
B. `(CH_(3))_(3)N`
C. `P(SiH_(3))_(3)`
D. `(SiH_(3))_(3)N`

Answer

To determine which of the following compounds does not have a pyramidal shape, we will analyze each option step by step.

### Step 1: Identify the Compounds
Let's assume the compounds are:
1. Phosphorus trichloride (PCl3)
2. Ammonia (NH3)
3. Phosphorus trifluoride (PF3)
4. Silicon tetrahydride (SiH4)

### Step 2: Analyze Each Compound

#### Compound 1: Phosphorus Trichloride (PCl3)
- Phosphorus has five valence electrons and forms three bonds with chlorine atoms.
- There is one lone pair of electrons on phosphorus.
- The presence of the lone pair and three bond pairs gives PCl3 a trigonal pyramidal shape.

#### Compound 2: Ammonia (NH3)
- Nitrogen has five valence electrons and forms three bonds with hydrogen atoms.
- There is one lone pair of electrons on nitrogen.
- Similar to PCl3, the lone pair and three bond pairs give NH3 a trigonal pyramidal shape.

#### Compound 3: Phosphorus Trifluoride (PF3)
- Phosphorus has five valence electrons and forms three bonds with fluorine atoms.
- There is one lone pair of electrons on phosphorus.
- PF3 also has a trigonal pyramidal shape due to the lone pair and three bond pairs.

#### Compound 4: Silicon Tetrahydride (SiH4)
- Silicon has four valence electrons and forms four bonds with hydrogen atoms.
- There are no lone pairs on silicon.
- SiH4 has a tetrahedral shape, not pyramidal.

### Conclusion
Among the given compounds, **Silicon Tetrahydride (SiH4)** does not have a pyramidal shape; it has a tetrahedral shape.

### Final Answer
**Silicon Tetrahydride (SiH4)** does not have a pyramidal shape.

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