Which of the following best explains why water (H_2O) is a polar molecule?

• A. Because water has a linear molecular geometry, causing the dipoles to cancel out.
• B. Because both hydrogen and oxygen have equal electronegativity, resulting in a nonpolar bond.
• C. Because hydrogen atoms attract electrons more strongly than oxygen.
• D. Because oxygen is more electronegative than hydrogen, creating an uneven distribution of electron density.

Answer: (D)

Verified step by step guidance

1. Recall that polarity in a molecule arises from differences in electronegativity between atoms and the shape of the molecule, which affects how dipole moments add up.
2. Identify the electronegativity values of oxygen and hydrogen: oxygen is significantly more electronegative than hydrogen, meaning it attracts shared electrons more strongly.
3. Understand that this difference in electronegativity creates polar covalent bonds, where the electron density is pulled closer to the oxygen atom, generating partial charges (δ- on oxygen and δ+ on hydrogens).
4. Consider the molecular geometry of water, which is bent (not linear) due to the two lone pairs on oxygen; this shape prevents the dipole moments from canceling out.
5. Conclude that the combination of oxygen's higher electronegativity and the bent shape of water leads to an uneven distribution of electron density, making water a polar molecule.