Why is water considered a polar molecule?
The correct answer and explanation is:
Water is considered a polar molecule due to the arrangement of its atoms and the distribution of charge within the molecule. The water molecule consists of two hydrogen atoms (H) and one oxygen atom (O). The oxygen atom is highly electronegative, meaning it has a strong attraction for electrons, while the hydrogen atoms have a much weaker electronegativity.
This difference in electronegativity creates a dipole moment within the molecule. The oxygen atom pulls the shared electrons in the covalent bonds toward itself, causing the oxygen end of the molecule to become slightly negative (δ-) and the hydrogen atoms to become slightly positive (δ+). This results in an uneven distribution of charge, which makes the water molecule polar.
Additionally, water has a bent or angular shape, not linear. The bond angle between the hydrogen-oxygen-hydrogen atoms is approximately 104.5 degrees. This bent shape contributes to the asymmetry of the molecule, further enhancing its polarity. If the molecule were linear, the individual bond dipoles would cancel out, and the molecule would not be polar.
The polarity of water gives it several important properties, such as its ability to dissolve many substances (its solvent properties), its high surface tension, and its relatively high boiling and melting points compared to other small molecules. These properties are a result of the hydrogen bonds that form between the positive hydrogen end of one water molecule and the negative oxygen end of another. The hydrogen bonds are relatively strong intermolecular forces that require significant energy to break, which is why water remains liquid at a wider range of temperatures compared to other small molecules.
In summary, water’s polarity arises from its molecular shape and the difference in electronegativity between oxygen and hydrogen atoms, leading to an uneven distribution of charge across the molecule.