Give the correct order of increasing electron gain enthalpy with negative sign for the elements O,S,F,Cl with reason
O < S < F < Cl
-1.48kJ mol-1 -2.0 kJ mol-1 -3.6 kJ mol-1 -3.8 kJ mol-1
Electron affinity generally becomes more negative on moving from left to right along a period. It is because on moving across a period, the atomic size decreases.
As a result, the force of attraction exerted by the nucleus on the electron increases.
Consequently, the atom has a greater tendency to gain an electron. Hence, electron gain enthalpy becomes more negative.
Cl has more negative electron gain enthalpy than fluorine because in it the added electron goes to the smaller energy shell(n=2) and hence suffers significant repulsion from the electrons already present in this shell. And fluorine also possesses high charge density.
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