ACS Chemistry Practice Exam 2025 – The All-in-One Guide to Exam Success!

In a polar bond, electrons are not shared equally between the two atoms involved. Instead, they are distributed in a way that favors the more electronegative atom. Electronegativity is a measure of an atom's ability to attract electrons in a bond. When two atoms with differing electronegativities form a bond, the electron density shifts toward the atom with the higher electronegativity.

This means that the electrons spend more time surrounding the more electronegative atom, which results in that atom acquiring a partial negative charge. Conversely, the atom with the lower electronegativity ends up with a partial positive charge. The unequal sharing of electrons is what defines a polar bond and gives rise to the dipole moment, where one end of the bond is slightly more negative and the other slightly more positive.

Understanding this distribution is crucial in predicting the behavior of molecules, their interactions, and their physical properties, such as boiling points and solubility.