Que: Arrange the following in each as instructed
(i) O, F, S, Cl, N in order of increasing strength of hydrogen bonding (X — H – X).
(ii) N2, O2, F2, Cl2 in increasing order of bond dissociation energy.
Ans: (i) Strength of hydrogen bonding depends on the electronegativity of the atom linked with hydrogen. Thus the order is S < Cl < N < O < F
(ii) The increasing order is F2 < Cl2 < O2 < N2. Both fluorine and chlorine atoms in F2 and Cl2 possess three non-bonded electron pairs each. Due to the small size of fluorine, there is larger repulsion between non-bonded electrons in comparison to chlorine. Thus, F2 has lesser dissociation energy than Cl2. In oxygen, two non-bonded electron pairs are present, i.e., less repulsion than Cl2 and in nitrogen only one electron pair is present, i.e., minimum repulsion is present. Hence, N2 has maximum stability.