Which of these 3 molecules is most polar? And which is the least polar? H2O, H2S, or SO2? Explain.
The Correct Answer and Explanation is:
Among the molecules H2O, H2S, and SO2, H2O (water) is the most polar, and H2S (hydrogen sulfide) is the least polar. Here’s the explanation:
Polarity Overview:
Polarity arises from the uneven distribution of electrons within a molecule, which leads to partial positive and negative charges at different regions. This uneven electron distribution typically occurs when atoms with different electronegativities are bonded together. If the molecule has an asymmetric shape, it leads to a net dipole moment, which defines its polarity.
Water (H2O):
Water is a highly polar molecule. The oxygen atom is much more electronegative than hydrogen, meaning it attracts electrons more strongly. As a result, the oxygen atom carries a partial negative charge, while the hydrogen atoms carry partial positive charges. The water molecule has a bent shape due to the two lone pairs of electrons on the oxygen atom, which further enhances the dipole moment. The strong hydrogen bonding between water molecules also contributes to its polarity. This makes water one of the most polar molecules in nature.
Sulfur Dioxide (SO2):
Sulfur dioxide is also a polar molecule. It has a bent shape due to the lone pairs on the sulfur atom. The oxygen atoms are more electronegative than sulfur, creating partial negative charges on the oxygen atoms and a partial positive charge on the sulfur atom. However, the electronegativity difference between sulfur and oxygen is smaller than between oxygen and hydrogen in water, and the dipole moment in SO2 is less pronounced than in water.
Hydrogen Sulfide (H2S):
Hydrogen sulfide is the least polar of these three molecules. Although it has a bent shape, similar to water and sulfur dioxide, the electronegativity difference between sulfur and hydrogen is much smaller than the difference between oxygen and hydrogen. Sulfur is only slightly more electronegative than hydrogen, leading to a much weaker dipole moment. As a result, H2S is less polar than both H2O and SO2.
Conclusion:
- Most Polar: H2O (water)
- Least Polar: H2S (hydrogen sulfide)
- Intermediate Polar: SO2 (sulfur dioxide)