Which of the following molecules behave as electrical dipoles ?
(i) `CCl_(4)` (ii) `CHCl_(3)` (iii) `BF_(3)` (iv) `H_(2)O` (v) `BeF_(2)` (vi) `NH_(3)`

Answer

To determine which of the given molecules behave as electrical dipoles, we need to analyze the molecular geometry and the distribution of electronegativity within each molecule. A molecule behaves as an electrical dipole if it has a net dipole moment, which occurs when there is an uneven distribution of electron density.

### Step-by-Step Solution:

1. **Analyze CCl₄ (Carbon Tetrachloride)**:
- **Geometry**: Tetrahedral
- **Electronegativity**: Chlorine is more electronegative than carbon, creating individual dipoles pointing towards the chlorine atoms.
- **Result**: The dipoles cancel each other due to symmetry.
- **Conclusion**: CCl₄ does not behave as an electrical dipole.

2. **Analyze CHCl₃ (Chloroform)**:
- **Geometry**: Tetrahedral
- **Electronegativity**: The molecule has one hydrogen and three chlorines. The dipoles from the three chlorines do not cancel out due to the presence of hydrogen.
- **Result**: There is a net dipole moment.
- **Conclusion**: CHCl₃ behaves as an electrical dipole.

3. **Analyze BF₃ (Boron Trifluoride)**:
- **Geometry**: Trigonal planar
- **Electronegativity**: The three fluorine atoms create dipoles pointing towards themselves.
- **Result**: The dipoles cancel each other out due to symmetry.
- **Conclusion**: BF₃ does not behave as an electrical dipole.

4. **Analyze H₂O (Water)**:
- **Geometry**: Bent (angular)
- **Electronegativity**: Oxygen is more electronegative than hydrogen, creating dipoles pointing towards oxygen.
- **Result**: The dipoles do not cancel out due to the bent shape.
- **Conclusion**: H₂O behaves as an electrical dipole.

5. **Analyze BeF₂ (Beryllium Fluoride)**:
- **Geometry**: Linear
- **Electronegativity**: The two fluorine atoms create dipoles pointing towards themselves.
- **Result**: The dipoles cancel each other due to linear symmetry.
- **Conclusion**: BeF₂ does not behave as an electrical dipole.

6. **Analyze NH₃ (Ammonia)**:
- **Geometry**: Trigonal pyramidal
- **Electronegativity**: The nitrogen atom is more electronegative than hydrogen, creating dipoles pointing towards nitrogen.
- **Result**: The dipoles do not cancel out due to the presence of a lone pair on nitrogen.
- **Conclusion**: NH₃ behaves as an electrical dipole.

### Final Summary:
The molecules that behave as electrical dipoles are:
- CHCl₃
- H₂O
- NH₃