Why does water evaporate at a higher temperature than nail polish remover does? Part of the answer lies in the strong bonds between hydrogen and oxygen in water molecules, as opposed to the weaker bonds between other elements in nail polish remover. But, how do we explain why a molecule like water has strong bonds between its atoms? We have to think of the ability of an element to attract electrons with a certain “pull”, known as electronegativity. Elements like oxygen, fluorine, and nitrogen tend to have high electronegativity values, so they exert more of a “pull” on electrons. Therefore, bonding elements like hydrogen and oxygen, as in the case of water, partly accounts for why water has a higher boiling point than many other substances, like acetone in rubbing alcohol, do.

When atoms of elements with high electronegativity values form bonds with atoms of other elements, a large electronegativity difference results. This electronegativity difference between the elements in the bond is used to determine the bond polarity, a quantity used to describe the sharing of electrons. Generally, a lower bond polarity refers to more equal sharing, while a higher bond polarity refers to more unequal sharing. 

First, try the practice questions to determine what you already know about electronegativity and its role in bond polarity. Then, watch the video lesson to learn more about bond polarity.