Question

The strongest hydrogen bonding is present in:

• A. $HF$
• B. $HCl$
• C. $HBr$
• D. $HI$

Answer 1

The correct option is A $HF$

The following conditions are to be satisfied for effective hydrogen bonding:
(i) Hydrogen atom should be bonded to a highly electronegative atom such as $F,O$ or $N$. Greater the electronegativity of the other atom, greater is the strength of the hydrogen bond. For example, the electronegativities of $F,O,N$ decrease as $F>O>N$. Consequently, the strength of H-bond decreases as

(ii) The size of the electronegative atom should be small. If the size of electronegative atom is large, its attractive force with the hydrogen atom would be less and consequently, the strength of H-bond will be reduced. For example, $N$ and $Cl$ has almost the same electronegativities but no hydrogen bonds are formed in the case of $H-Cl$ because of the larger size of $Cl$ atom.