What is the significance of an electronegativity difference of 1.7 between 2 atoms?

Explanation:

Electronegativity is defined as the ability of an atom to attract electrons towards itself.

Whereas when there is difference in values electronegativity of two different atoms then it is known as electronegativity difference.

For example, in a HCl compound the hydrogen atom is electropositive and chlorine atom is electronegative. Electronegativity value of hydrogen is 2.1 and chlorine has 3.0.

Hence, difference in their electronegativities is 3.0 - 2.1 = 0.9.

Also, it is known that when the electronegativity difference is less than or equal to 1.7 then the bond formed between the combining atoms will be polar covalent.

a polar bond is formed when electrons are shared unevenly between atoms