Which of the following best describes the difference between a polar molecule and a nonpolar molecule?

• A. A polar molecule has an uneven distribution of electron density, resulting in a permanent dipole moment, while a nonpolar molecule has an even distribution of electron density and no permanent dipole.
• B. A polar molecule is always larger in size than a nonpolar molecule.
• C. A polar molecule contains only ionic bonds, while a nonpolar molecule contains only covalent bonds.
• D. A polar molecule cannot participate in hydrogen bonding, while a nonpolar molecule can.

Answer: (A)

Verified step by step guidance

1. Understand that polarity in molecules arises from the distribution of electron density within the molecule.
2. Recognize that a polar molecule has an uneven distribution of electron density, which creates regions of partial positive and partial negative charge, leading to a permanent dipole moment.
3. Know that a nonpolar molecule has an even distribution of electron density, meaning there is no separation of charge and no permanent dipole moment.
4. Recall that molecular polarity depends on both the polarity of individual bonds and the geometry (shape) of the molecule, which affects how bond dipoles add up.
5. Use this understanding to evaluate the given options and identify that the correct description involves the difference in electron density distribution and the presence or absence of a permanent dipole moment.