The electronic configurations of four elements are given below. Arrange these elements in the correct order of the magnitude (without sign) of their electron affinity
(i) `2s^(2)2p^(5)` (ii) `3s^(2)3p^(5)`
(iii) `2s^(2)2p^(4)` (iv) `3s^(2)3p^(4)`
Select the correct answer using the codes given below:

Options

A. `(ii) lt (i) lt (iv) lt(iii)`
B. `(i) lt (iii) lt (iv) lt (ii)`
C. `(i) lt (ii) lt (iv) lt (iii)`
D. `(iii) lt (iv) lt (i) lt (ii)`

Answer

D

Explanation

In general, electron affinity increase across the period account of increase of `Z_(eff)` while decreases on moving down the group on account of increase of size. Elements (i) and (ii) are succeding members of the `2nd` period and belong to groups `17` and `16` respectively, while elements (ii) and (iv) are succeeding members of teh `3rd` period and belong to groups `17` and `16`, respectively. (i) is `F`, (ii) is `C1`, (iii) is `O`, while (iv) is `S`.
However, `O` and `F` have unexpectedly low electron affinities on account of relatively small size.

Thus, the correct order of electron affinity is
`O lt S lt F lt C1`
i.e., `(iii) lt (iv) lt (i) lt (ii)`