Under what conditions does polar covalence occur?

Polar covalence occurs when there is a significant difference in electronegativity between the two atoms involved in a bond, leading to an unequal sharing of electrons. The correct context for polar covalent bonds is characterized by an electronegativity difference that typically falls between 0.4 and 1.7.

When the electronegativity difference is greater than about 1.7, the bond tends to become ionic rather than covalent, as the more electronegative atom attracts the shared electrons so strongly that it effectively gains an electron from the less electronegative atom. Therefore, option C, which specifies a difference that suggests polar covalence, accurately describes the range where polar covalent bonds are formed. This range is crucial because it captures the behavior of electron sharing in such bonds, where atoms do not completely transfer electrons, but rather share them in a skewed manner, resulting in partial positive and negative charges.

Overall, recognizing the appropriate electronegativity difference is key to understanding the nature of the bond formed between two atoms and is fundamental to predicting the properties of the resulting molecule.