In which of the following molecules all the atoms lie in one plane ? .

Options

A. `CH_(4)`
B. `BF_(3)`
C. `PF_(5)`
D. `NH_(3)`

Explanation

To determine which of the given molecules has all its atoms lying in one plane, we will analyze each molecule based on its hybridization and molecular geometry.

### Step-by-Step Solution:

1. **Analyze CH4 (Methane)**:
- The carbon atom in CH4 is sp³ hybridized.
- In sp³ hybridization, the geometry is tetrahedral.
- This means that the four hydrogen atoms are not in the same plane; they are arranged in three-dimensional space.
- **Conclusion**: CH4 does not have all atoms in one plane.

2. **Analyze BF3 (Boron Trifluoride)**:
- The boron atom in BF3 is sp² hybridized.
- In sp² hybridization, the geometry is trigonal planar.
- This means that the three fluorine atoms are arranged in the same plane with bond angles of 120 degrees.
- **Conclusion**: BF3 has all atoms in one plane.

3. **Analyze PF5 (Phosphorus Pentafluoride)**:
- The phosphorus atom in PF5 is sp³d hybridized.
- The geometry is trigonal bipyramidal.
- In this structure, there are two fluorine atoms positioned above and below the plane of the three fluorine atoms, which lie in a plane.
- **Conclusion**: PF5 does not have all atoms in one plane.

4. **Analyze NH3 (Ammonia)**:
- The nitrogen atom in NH3 is sp³ hybridized.
- The geometry is also tetrahedral.
- NH3 has one lone pair and three hydrogen atoms, which means that the hydrogen atoms are not all in the same plane.
- **Conclusion**: NH3 does not have all atoms in one plane.

### Final Answer:
The molecule in which all the atoms lie in one plane is **BF3**.

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