The increasing order of electron affinity of the electronic configuration of element is :
(I) `1s^(2)2s^(2)2p^(6)3s^(2)3p^(5)`
(II) `1s^(2)2s^(2)2p^(3)`
(III) `1s^(2)2s^(2)2p^(5)`
(I) `1s^(2)2s^(2)2p^(6)3s^(1)`

Options

A. `II lt IV lt III lt I`
B. `I lt II lt III lt IV`
C. `I lt III lt II lt IV`
D. `IV lt III lt II lt I`

Answer

To determine the increasing order of electron affinity for the given electronic configurations, we need to analyze each configuration and understand how stable they are when an electron is added. Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gas phase. Generally, elements with half-filled or fully filled subshells have lower electron affinities due to their stability.

Let's analyze the given electronic configurations:

1. **(I) `1s^(2)2s^(2)2p^(6)3s^(2)3p^(5)`**:
- This configuration corresponds to an element in Group 17 (halogens). When an electron is added, it achieves a stable noble gas configuration (`3p^6`). Thus, it has a high electron affinity.

2. **(II) `1s^(2)2s^(2)2p^(3)`**:
- This configuration corresponds to an element in Group 15 (nitrogen group). It has a half-filled `2p` subshell. Adding an electron to this configuration will require more energy due to the stability of the half-filled subshell. Hence, it has a lower electron affinity compared to the first configuration.

3. **(III) `1s^(2)2s^(2)2p^(5)`**:
- This configuration corresponds to an element in Group 17 (halogens). When an electron is added, it achieves a stable noble gas configuration (`2p^6`). Thus, it has a high electron affinity, but not as high as the first configuration because it is already close to a stable state.

4. **(IV) `1s^(2)2s^(2)2p^(6)3s^(1)`**:
- This configuration corresponds to an element in Group 1 (alkali metals). When an electron is added, it moves to a higher energy level, which is less stable compared to the previous configurations. Therefore, it has the lowest electron affinity.

Now, we can summarize the electron affinities in increasing order:

- **(IV)** `1s^(2)2s^(2)2p^(6)3s^(1)` (lowest electron affinity)
- **(II)** `1s^(2)2s^(2)2p^(3)`
- **(III)** `1s^(2)2s^(2)2p^(5)`
- **(I)** `1s^(2)2s^(2)2p^(6)3s^(2)3p^(5)` (highest electron affinity)

Thus, the increasing order of electron affinity is:
**(IV) < (II) < (III) < (I)**