How does electronegativity affect ionic bonding?

Hint: Ionic bond is formed when transfer of valence electrons occur. The compounds formed from this bond are called ionic compounds. Electronegativity of any element is the property to attract a shared pair of electrons. electronegativity increases from left to right in a period.

Complete answer: Electronegativity of any element is its ability to attract electrons of other elements in a molecule and form bonds. This electronegativity of elements increases as we move from left to right in a period. This means that metals, which are at extreme left are less electronegative, while non metals (till group 17) that are at the right in a period are more electronegative.
As we know when a metal and a nonmetal are involved in a compound, then ionic bonds are formed. Electronegativity of the atoms involved in a compound affects the ionic bonds. More electronegative elements have the tendency to form higher ionic character bonds with other elements.
Elements that have high electronegativity, will form a bond with any atom that has more ionic character. This can be explained through fluorine. Fluorine is the most electronegative element; it bonds with other atoms to create ionic bonds due to electron transfer. With metal like sodium, it forms NaF which is an ionic compound formed from transfer of valence electrons from Na to F. While in NF, the bonds formed are half ionic and half covalent. However, when fluorine bonds with itself to form ${{F}_{2}}$, the bond is completely covalent.
Through this, it can be inferred that electronegativity of the atoms, strengthens or weakens the ionic character in a bond.
Hence, when a more electronegative atom is bonded with a less electronegative atom (mainly metals), then ionic character of the bond is the highest. While, when the electronegativity value of atoms does not have much difference, the ionic character of the bond decreases.

Note: Strong ionic bonds will be seen in compounds of halogens (group 17) and that of alkali metals (group 1). This is due to large electronegativity differences between them.