In which of the following options order of arrangement does not agree with the variation of property indicated against it?
(i) Al3+< Mg2+< Na+ < F– (increasing ionic size)
(ii) B < C < N < O (increasing first ionisation enthalpy)
(iii) I < Br < Cl < F (increasing electron gain enthalpy)
(iv) Li < Na < K < Rb (increasing metallic radius)
The answer is the option (ii) and (iii)
Explanation: The ionisation enthalpy of N is always higher than that of O due to greater stability of half-filled electronic configuration of oxygen. So (ii) is incorrect. Similarly, in option (iii), the electron gain enthalpy of F is lower than that of Cl due to the small size of F. Hence option (iii) is also wrong.