How is a molecules polarity is related to its electron density?

A molecule's polarity is determined by the distribution of electron density across its bonds. When there is an unequal sharing of electrons between atoms with different electronegativities, the more electronegative atom attracts electron density closer to itself, creating a dipole moment. This results in a polar molecule, which has distinct positive and negative regions. Conversely, if electron density is evenly distributed, the molecule is nonpolar.