Which is not the correct order for the stated property?

Which is not the correct order for the stated property?
  1. $\mathrm{Ba}>\mathrm{Sr}>\mathrm{Mg} ;$ atomic radius
  2. $\mathrm{F}>\mathrm{O}>\mathrm{N}$; first ionization enthalpy
  3. $\mathrm{Cl}>\mathrm{F}>\mathrm{I} ;$ electron affinity
  4. $\mathrm{O}>\mathrm{Se}>$ Te $;$ electronegativity

Solution

On moving along the period, ionization enthalpy increases. In second period, the order of ionization enthalpy should be as follows:
$\mathrm{F}>\mathrm{O}>\mathrm{N}$
But N has half-filled structure, therefore, it is more stable than $\mathrm{O}$. That is why its ionization enthalpy is higher than $\mathrm{O}$. Thus, the correct order of IE is
$\mathrm{F}>\mathrm{N}>\mathrm{O}$

Asked in: JEE-TOPICTESTS-CHEMISTRY

Practice more CLASSIFICATION OF ELEMENTS AND PERIODICITY IN PROPERTIES questions on Aicharya