Question

The correct order of electron gain enthalpy $(\Delta _{eg}H)$ of the halogen atoms is

• A. $F < Cl < Br < I$
• B. $Cl < F < Br < I$
• C. $I < Br < Cl < F$
• D. $Cl < Br < I < F$

Answer 1

Answer: (B)

$Cl < F < Br < I$

Answer 2

The correct order of electron gain enthalpy $\Delta H$ (with $+$ sign) of the halogen atom is $Cl < F < Br < I$ The reason that fluorine has a less negative electron affinity than chlorine is relatively small size of F atom resulting in the repulsions (electron-electron) to the entering electron.