Question

Electronic configurations of four elements A, B, C, and D are given below: \[ {A: } 1s^2 2s^2 2p^4, \quad {B: } 1s^2 2s^2 2p^6 3s^1, \quad {C: } 1s^2 2s^2 2p^6, \quad {D: } 1s^2 2s^2 2p^5 \] The correct order of increasing tendency to gain electrons is: 
 

• A. C<A<B<D
• B. D<A<B<C
• C. D<C<B<A
• D. C<B<A<D

Hint:

Elements closer to achieving a full outer electron shell typically have a higher tendency to gain electrons, with halogens being a prime example due to needing only one additional electron.

Answer 1

The Correct Option is D

The tendency to gain electrons increases with the number of electrons needed to achieve a stable noble gas configuration. Evaluating the configurations:
- C (\(1s^2 2s^2 2p^6\)) is already at a noble gas configuration, so it has no tendency to gain electrons.
- B (\(1s^2 2s^2 2p^6 3s^1\)) needs to lose one electron to reach a noble gas configuration, indicating a very low tendency to gain.
- A (\(1s^2 2s^2 2p^4\)) needs two electrons to fill its p orbitals, showing a higher tendency to gain electrons than B.
- D (\(1s^2 2s^2 2p^5\)) needs only one electron to achieve a full p orbital, indicating the highest tendency to gain electrons.
Hence, the order is C<B<A<D.