The least stable ion is

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(B) The electronic configuration of $Li$ $(Z=3)$ is $1s^2 \, 2s^1$. Adding one electron forms $Li^-$ $(1s^2 \, 2s^2)$,which is stable due to a fully f

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$Be^{-}$

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(B) The electronic configuration of $Li$ $(Z=3)$ is $1s^2 \, 2s^1$. Adding one electron forms $Li^-$ $(1s^2 \, 2s^2)$,which is stable due to a fully filled $2s$ subshell.The electronic configuration of $Be$ $(Z=4)$ is $1s^2 \, 2s^2$. Adding one electron forms $Be^-$ $(1s^2 \, 2s^2 \, 2p^1)$. This process disrupts the stable,fully filled $2s^2$ configuration of $Be$,making $Be^-$ the least stable ion.The electronic configuration of $B$ $(Z=5)$ is $1s^2 \, 2s^2 \, 2p^1$. Adding one electron forms $B^-$ $(1s^2 \, 2s^2 \, 2p^2)$,which is relatively stable.The electronic configuration of $C$ $(Z=6)$ is $1s^2 \, 2s^2 \, 2p^2$. Adding one electron forms $C^-$ $(1s^2 \, 2s^2 \, 2p^3)$,which is stable due to the half-filled $p$-subshell.

Similar Questions

Which of the following arrangements for the three halogens $Cl$,$Br$,and $I$ when placed in the order of their increasing electron affinity is correct?

Which of the following statements is incorrect?

Which elements show an anomalous trend in the negative value of electron gain enthalpy within their respective groups?

Which of the following represents the correct order of increasing electron gain enthalpy (with negative sign) for the elements?
$a.$ Nitrogen
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The order of negative electron gain enthalpy of $Li$,$Na$,$S$,$Cl$ is

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