The pyramidal geometry is associated with :

Options

A. `CH_(4)`
B. `NH_(3)`
C. `H_(2)O`
D. `CO_(2)`

Explanation

To determine which molecule has a pyramidal geometry, we can analyze the molecular geometries of the given compounds: CH4, NH3, H2O, and CO2.

### Step-by-Step Solution:

1. **Identify the Valence Electrons**:
- **CH4 (Methane)**: Carbon has 4 valence electrons. It forms 4 single bonds with hydrogen atoms.
- **NH3 (Ammonia)**: Nitrogen has 5 valence electrons. It forms 3 single bonds with hydrogen atoms and has 1 lone pair.
- **H2O (Water)**: Oxygen has 6 valence electrons. It forms 2 single bonds with hydrogen atoms and has 2 lone pairs.
- **CO2 (Carbon Dioxide)**: Carbon has 4 valence electrons. It forms 2 double bonds with oxygen atoms.

2. **Determine the Molecular Geometry**:
- **CH4**: The geometry is tetrahedral due to the four bond pairs and no lone pairs.
- **NH3**: The geometry is trigonal pyramidal because there are three bond pairs and one lone pair, which pushes the hydrogen atoms down, creating a pyramid shape.
- **H2O**: The geometry is bent or V-shaped due to two bond pairs and two lone pairs, which repel each other.
- **CO2**: The geometry is linear because there are two double bonds and no lone pairs.

3. **Conclusion**:
- Among the given compounds, only **NH3 (Ammonia)** has a pyramidal geometry.

### Final Answer:
The pyramidal geometry is associated with **NH3 (Ammonia)**.

---