Question

Which is the more polar bond in each of the following pairs from Problem 9.61: (a) or (b); (c) or (d); (e) or (f)?

Short answer

The disparity in electronegativity between the two atoms that comprise a bond determines its polarity.

Step-by-step solution

Lewis structures for covalently bonded compounds

Bonds are depicted as lines. Lone pair electrons are pairs of dots. All atoms (except H) desire eight electrons (octet rule) Typically, an atom will form one bond for each electron. The premise of the Central Atom: The central atom is the least electronegative (except hydrogen, it only has one electron)

Difference between polar bonds in each of the following pairs 

(a) N $\mathbf{\leftarrow }$ B= ΔEN = 1

(b) N $\mathbf{\to }$ O= ΔEN = 0.4

(c) C $\mathbf{\to }$ S= ΔEN = 0.03

(d) S $\mathbf{\to }$ O= ΔEN = 0.86

(e) N $\mathbf{\leftarrow }$ H= ΔEN = 0.84

(f) Cl $\mathbf{\to }$ O= ΔEN = 0.28

Thus, N-B has more polar bond.