What does a difference in electronegativity between bonded atoms indicate?

A difference in electronegativity between bonded atoms indicates the degree of ionic character in the bond. When two atoms form a bond, their electronegativities help to determine how the electrons are shared between them. If one atom is significantly more electronegative than the other, it will attract the bonding electrons more strongly, leading to an unequal sharing of electrons. This results in partial positive and negative charges on the atoms, creating a polar bond. The greater the difference in electronegativity, the more ionic character the bond will exhibit, potentially leading to the formation of ionic compounds if the difference is large enough.

In contrast, the other options relate to chemical properties but do not directly connect to electronegativity's role in bonding. The atoms' mass difference, size, and atomic radius are important in understanding various characteristics of elements, but they do not directly describe the implications of different electronegativities in bonded atoms.