Question

Which of the bonds in the Problem 9.85 is the least polar?

Short answer

The Si-F bond is least polar bond.

Step-by-step solution

Bond Polarity

Polarity of a bond decreases as the electronegativity difference between the atoms decreases.

The electronegativity difference in Hg-I bond is$\mathbf{(}\mathbf{2}.\mathbf{2}-\mathbf{1}.\mathbf{5}\mathbf{)}=\mathbf{0}.\mathbf{7}$

The electronegativity difference in P - I bond is$\mathbf{(}\mathbf{2}.\mathbf{2}-\mathbf{1}.\mathbf{8}\mathbf{)}=\mathbf{0}.\mathbf{4}$

The electronegativity difference in Si- F bond is$\mathbf{(}\mathbf{2}.\mathbf{2}-\mathbf{2}.\mathbf{1}\mathbf{)}=\mathbf{0}.\mathbf{1}$

The electronegativity difference in Mg –N bond is$\mathbf{(}\mathbf{3}.\mathbf{1}-\mathbf{1}.\mathbf{3}\mathbf{)}=\mathbf{1}.\mathbf{8}$

Least polar bond 

The electronegativity difference in Si-F bond is minimum among the four at = (2.2-2.1) = 0.1

The Si-F bond is least polar bond.