Which of the following molecules behave as electrical dipoles ?
(i) `C Cl_(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 polarity of each molecule. An electrical dipole occurs when there is a separation of positive and negative charges within a molecule, leading to a net dipole moment.

### Step-by-step Solution:

1. **Analyze CCl₄ (Carbon Tetrachloride)**:
- Structure: Tetrahedral geometry with four Cl atoms bonded to C.
- Polarity: Each C-Cl bond is polar due to the electronegativity difference between C and Cl. However, the symmetrical arrangement causes the dipoles to cancel each other out.
- **Conclusion**: CCl₄ does not behave as an electrical dipole (Dipole moment = 0).

2. **Analyze CHCl₃ (Chloroform)**:
- Structure: Tetrahedral geometry with one H atom and three Cl atoms bonded to C.
- Polarity: The C-H bond is less polar than the C-Cl bonds. The dipoles from the three C-Cl bonds do not completely cancel due to the presence of the hydrogen atom.
- **Conclusion**: CHCl₃ behaves as an electrical dipole (Dipole moment ≠ 0).

3. **Analyze BF₃ (Boron Trifluoride)**:
- Structure: Trigonal planar geometry with three F atoms bonded to B.
- Polarity: Each B-F bond is polar, but the symmetrical arrangement leads to cancellation of dipole moments.
- **Conclusion**: BF₃ does not behave as an electrical dipole (Dipole moment = 0).

4. **Analyze H₂O (Water)**:
- Structure: Bent geometry with two H atoms and two lone pairs on O.
- Polarity: The O-H bonds are polar, and the bent shape prevents cancellation of dipole moments.
- **Conclusion**: H₂O behaves as an electrical dipole (Dipole moment ≠ 0).

5. **Analyze BeF₂ (Beryllium Fluoride)**:
- Structure: Linear geometry with two F atoms bonded to Be.
- Polarity: Each Be-F bond is polar, but the linear arrangement causes the dipoles to cancel out.
- **Conclusion**: BeF₂ does not behave as an electrical dipole (Dipole moment = 0).

6. **Analyze NH₃ (Ammonia)**:
- Structure: Trigonal pyramidal geometry with one lone pair on N and three H atoms.
- Polarity: The N-H bonds are polar, and the lone pair creates an asymmetrical shape, leading to a net dipole moment.
- **Conclusion**: NH₃ behaves as an electrical dipole (Dipole moment ≠ 0).

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