Answer
If the difference in electronegativities of the two atoms is large, then the bond is ionic; however, if the difference in electronegativities of the two atoms is small, then the bond is covalent.
Work Step by Step
If the difference in electronegativities of the atoms is greater than 2.0, then the bond is most likely ionic, meaning that the electrons are completely transferred from one atom to the other.
If the difference in electronegativities of the atoms is less than 2.0, then the bond is most likely covalent, meaning that the electrons are shared between the atoms. If the difference is less than 0.4, the bond is completely covalent, which means that the two atoms share the electrons equally between them. Electronegativity differences between 0.4 and 2.0 represents a covalent bond where the electron sharing is not equal between the two atoms.
