Question

Identify the least stable ion amongst the following:

• A. $L{i}^{–}$
• B. $B{e}^{-}$
• C. $B^{-}$
• D. $C^{–}$

Answer 1

The correct option is B $B{e}^{-}$

(a) For $L{i}^{-}$ electronic configuration is $1s^{2}2s^2$ i.e., stable configuration.
(b) In $B{e}^{-}$ electron is added to $2p$ orbital. The stable configuration of $1s^{2}2s^2$ is disturbed.
(c) Electronic configuration of $B^{-}$ is $1s^{2}2s^{2}2p^2$, electron is added into same subshell.
(d) For $C^{-}$ electronic configuration is $1s^{2}2s^{2}2p^3$ which is very stable configuration.