Why is water (H_2O) called a polar molecule?

• A. Because its molecular shape is linear, causing the dipoles to cancel out.
• B. Because it is composed of two different elements.
• C. Because it has a bent molecular shape and an uneven distribution of electron density, resulting in a net dipole moment.
• D. Because both hydrogen and oxygen atoms have the same electronegativity, leading to equal sharing of electrons.

Answer: (C)

Verified step by step guidance

1. Understand that polarity in molecules arises from differences in electronegativity between atoms and the shape of the molecule, which affects how dipole moments add up.
2. Recognize that oxygen is more electronegative than hydrogen, so the O-H bonds are polar with a partial negative charge on oxygen and partial positive charges on hydrogens.
3. Identify the molecular geometry of water, which is bent (angular) due to the two lone pairs on oxygen, not linear.
4. Realize that because of the bent shape, the individual bond dipoles do not cancel out but instead combine to create a net dipole moment.
5. Conclude that the combination of polar O-H bonds and the bent shape leads to an uneven distribution of electron density, making water a polar molecule.