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

• A. Water has a bent molecular geometry and an uneven distribution of electron density due to the difference in electronegativity between hydrogen and oxygen.
• B. Water has a linear molecular geometry.
• C. Water molecules have equal sharing of electrons between hydrogen and oxygen atoms.
• D. Water is composed of nonpolar covalent bonds.

Answer: (A)

Verified step by step guidance

1. Recall that molecular polarity depends on both the shape (geometry) of the molecule and the difference in electronegativity between the atoms involved.
2. Identify the molecular geometry of water (H\_2O). Water has two hydrogen atoms bonded to oxygen and two lone pairs on oxygen, resulting in a bent (angular) shape rather than a linear shape.
3. Understand that oxygen is more electronegative than hydrogen, which causes the electrons in the O-H bonds to be shared unequally, creating partial negative charges near oxygen and partial positive charges near hydrogen.
4. Recognize that because of the bent shape, the dipole moments of the two O-H bonds do not cancel out, leading to an overall molecular dipole moment, making water a polar molecule.
5. Conclude that the combination of bent molecular geometry and the difference in electronegativity between oxygen and hydrogen explains why water is polar, unlike molecules with linear geometry or nonpolar covalent bonds.