Which of the following molecules is the least polar? A) H-H

B) H-CI

C) H-F

D) H-I

A) H-H is least polar

Explanation:

Electronegativity is defined as the property of an element to attract a shared pair of electron towards itself. The more is the difference in electronegativity, the more polat the bond is.

1. H-H : Electronegativity difference = electronegativity of hydrogen - electronegativity of hydrogen =2.1 -2.1= 0

2.   H-Cl : Electronegativity difference = electronegativity of chlorine - electronegativity of hydrogen = 3-2.1 = 0.9

3. H-F : Electronegativity difference  = electronegativity of fluorine - electronegativity of hydrogen= 4-2.1= 1.9  

4.   H-I : Electronegativity difference = electronegativity of iodine - electronegativity of hydrogen= 2.5 -2.1= 0.4

Thus the least electronegativity difference between the bonded atoms is in H-H , this is least polar.