In which of the following arrangements, the order is according to the property indicated against it?

Options

A. `F_(2) gt Cl_(2) gt Br_(2) gt I_(2)` Oxidising agent
B. `NH_(3) gt PH_(3) gt AsH_3 gt SbH_(3) gt BiH_(3)` Basic property
C. `F gt Cl gt Br gt I` Electron gain enthalpy
D. `C gt Si gt Ge gt Sn` Ability to form `p pi-dpi` bond

Answer

C

Explanation

The correct electron gain enthalpy trend is
`{:(,"Cl",gt,F,gt,Br,gt,I),("kJ/ mol",-349,,-328,,-325,,-295):}`
Fluorine has less electron gain enthalpy than chlorine due to exceptionally small size of fluorine which leads to strong inter-electronic repulsion when an extra electron is added to these atoms i.e., electron density is high and the addition of an electron is not easy. the electron gain enthalpy of bromine is only very slightly less than fluorine due to bigger size of bromine atom, the effective nuclear charge on the incoming electron is much less.