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

• A. Water has a linear molecular geometry, resulting in a dipole moment.
• B. Hydrogen atoms in water have a greater electron density than the oxygen atom.
• C. Oxygen is more electronegative than hydrogen, causing an unequal sharing of electrons.
• D. Water molecules are held together by ionic bonds.

Answer: (C)

Verified step by step guidance

1. Understand the concept of molecular polarity: A molecule is polar if it has an uneven distribution of electron density, resulting in a dipole moment.
2. Recall that electronegativity is the tendency of an atom to attract electrons in a bond. When two atoms have different electronegativities, the electrons are shared unequally.
3. Analyze the water molecule (H\_2O): Oxygen is more electronegative than hydrogen, so it pulls the shared electrons closer to itself, creating partial negative and positive charges.
4. Consider the molecular geometry of water: It is bent (not linear), which means the dipole moments from the O-H bonds do not cancel out, resulting in an overall polar molecule.
5. Conclude that the polarity of water arises because oxygen's higher electronegativity causes unequal sharing of electrons, combined with the bent shape that prevents dipole cancellation.