Question

Increasing strength of H- bonding ($X--H-X$) in S, O, F, Cl, N is:
(A) $Cl < S < N < O < F$
(B) $N < Cl < S < O < F$
(C) $S < Cl < N < O < F$
(D) $S < N < Cl < O < F$

Answer 1

The strength of the hydrogen bond formed will depend upon the electronegativity difference between the atom and hydrogen atom .Thus by arranging the given elements on the basis of electronegativity we would be able to arrange them in the increasing strength of H- bonding.

Complete step by step answer:
- Let's start with the concept of hydrogen bonding. It is the electromagnetic force of attraction created between a nearby electronegative atom and another partially positively charged hydrogen atom attached to a highly electronegative atom. It’s not a true chemical bond, it’s a kind of dipole-dipole interaction.
- The hydrogen bonding or these forces of attraction can occur within different parts of a single molecule (intramolecular) or between different molecules (Intermolecular).
-The hydrogen acceptor is an ion that contains a lone pair that participates in the hydrogen bond or an electronegative atom of a neighboring molecule and the donor in a hydrogen bond is usually a strongly electronegative atom such as fluorine, oxygen, or nitrogen which is covalently bonded to a hydrogen bond.
- In this respect, electronegativity should be high for better hydrogen bonding, and the size of the atom should be small. Better the hydrogen bonding, higher will be the bond strength.
- Among the given elements S, O, F, Cl, N as we know fluorine has the highest electronegativity, followed by oxygen, nitrogen, chlorine and the electronegativity will be smaller for sulphur.
- As we mentioned above, the more electronegative the element, more is the bond strength of hydrogen bonding. Hence the increasing order of bond strength will be $S < Cl < N < O < F$.
So, the correct answer is “Option C”.

Note: Keep in mind that the hydrogen bonding cannot occur without significant differences in electronegativity between the atom it is bonded to and hydrogen atom. For example the molecules such as$P{{H}_{3}}$, do no not partake in hydrogen bonding due to the similarity in the electronegativities of phosphorus and hydrogen. Both these atoms have an electronegativity of 2.1 and hence no dipole moment occurs and as a result no hydrogen bonding.