Answer: Option (a) is the correct answer.
Explanation:
An ionic bond is formed by transfer of electrons between the two chemically combining atoms. Whereas a covalent bond is defined as the bond formed by sharing of electrons between the two chemically combining atoms.
When electronegativity difference is from 0.0 to 0.4 then bond formed between the two atoms is non-polar covalent in nature.
When electronegativity difference is greater than 0.4 and less than 1.7 then bond between the two atoms is a polar covalent bond.
When electronegativity difference is 1.7 or greater than the bond formed is ionic in nature.
Thus, we can conclude that ionic type of bond has an electronegativity difference greater than 1.7.
