Question

Which one of the following arrangements
represents the correct order of electron gain
enthalpy (with negative sign) of the given
atomic species?
(a) S < O < Cl < F (b) Cl < F < S < O
(c) F < Cl < O < S (d) O < S < F < Cl

Answer 1

Answer:

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Answer 2

(c) F < Cl < O < S

Explanation:

Halogens have high electron affinity because they have 7 electrons in their outer shell. So they have the tendency to gain one electron and achieve the stable octet structure. Electron affinity increases along a period and decreases on moving down a group.

The value of electron gain enthalpies for the elements are Cl = 349, F = 333, S = 200, O = 142.

The E.A. of F is less than Cl and that of  O is less than S, because fluorine & oxygen atoms are smaller in size, so the incoming electron is added to space already crowded with electrons and will thereby experience strong repulsion.

Option C is the answer.