S C Kheterpal, S N Dhawan and, P N Kapil Solutions for Chapter: Classification of Elements and Periodicity in Properties, Exercise 6: PROBLEMS FOR PRACTICE

Arrange the elements with the following electronic configuration in order of increasing electron gain enthalpy.
(i) $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^5$ (ii) $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^4$ (iii) $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^3$ (iv) $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^4$

Arrange the following elements in order of decreasing electron gain enthalpy:

$\mathrm{B}, \mathrm{C}, \mathrm{N}$ and $\mathrm{O}$

The electron gain enthalpies of halogens decreases in the order of $\mathrm{F}>\mathrm{Cl}>\mathrm{Br}>\mathrm{I}$ comment upon statement.