Question

In which of the following options the order of arrangement does not agree with the variation of property indicated against it?

(a) ${I}<{Br}<{Cl}<{F}$ (increasing electron gain enthalpy)

(b) ${Li}<{Na}<{K}<{Rb}$ (increasing metallic radius)

(c) ${Al}^{3+}<{Mg}^{2+}<{Na}^{+}<{F}^{-}$(increasing ionic size)

(d) ${B}<{C}<{N}<{O}$ (increasing first ionisation enthalpy)

Answer 1

In fluorine, due to its small size incoming electron will experience more repulsion from the valence electrons thus, it has lower negative electron gain enthalpy than chlorine.

The correct order of increasing negative electron gain enthalpy is : ${I}<{Br}<{F}<{Cl}$ and the correct order of increasing first ionization enthalpy is ${B}<{C}<{O}<{N}$ due to half filled orbital of nitrogen which provides extra stability to valence electrons of nitrogen.

So, The correct option of this question will be (a) & (d)