What primarily determines the polarity of a bond?

The polarity of a bond is primarily determined by electronegativity, which is the ability of an atom to attract electrons in a chemical bond. When two atoms in a bond have differing electronegativities, the shared electrons are pulled more toward the atom with the higher electronegativity. This creates a dipole moment, resulting in a polar bond where one end of the bond becomes slightly negative and the other end becomes slightly positive.

In contrast, options such as atomic mass, molecular weight, and bond length do not directly influence the charge distribution in a bond. Atomic mass relates to the mass of a single atom and does not determine how electrons are shared. Molecular weight is the total weight of a molecule but does not affect the electronegative interactions between atoms. Bond length refers to the distance between atoms in a bond and can indirectly relate to bond strength and polarity, but it is not the primary factor that determines a bond's polarity. Thus, the concept of electronegativity is central to understanding and predicting bond polarity.