Question

Polar molecules are the molecules:

• A. having zero dipole moment
• B. acquire a dipole moment only in the presence of electric field due to displacement of charges
• C. acquire a dipole moment only when magnetic field is absent
• D. having a permanent electric dipole moment

Answer 1

The Correct Option is D

To determine the correct answer, we need to understand the concept of polar molecules in the realm of physics and chemistry.

Polar Molecules: A polar molecule is characterized by having a molecular structure where the distribution of electrons between the covalently bonded atoms is uneven. This happens because of differences in electronegativity. Thus, polar molecules possess a permanent electric dipole moment. 

Let's evaluate the given options:

1. Option 1: Having zero dipole moment
   • This describes non-polar molecules. Therefore, this is incorrect for polar molecules.
2. Option 2: Acquire a dipole moment only in the presence of an electric field due to the displacement of charges
   • This describes induced dipoles, not inherent polar molecules. Hence, this is incorrect.
3. Option 3: Acquire a dipole moment only when the magnetic field is absent
   • This is unrelated to the behavior of electric dipoles in molecules; magnetic fields generally do not define polarity in chemistry. Thus, it is incorrect.
4. Option 4: Having a permanent electric dipole moment
   • This precisely defines polar molecules, making this the correct choice.

Conclusion: The correct answer is that polar molecules are those having a permanent electric dipole moment.