Question

Which of the following has highest second ionization energy?

• A. $Ni$
• B. $V$
• C. $Cr$
• D. $Mn$

Answer 1

Answer: (C)

$Cr$

Electronic configuration of chromium is ${1s}^2{2s}^2{2p}^6{3s}^2{3p}^6{3d}^5{4s}^1$

We can remove the $1^{st}$ $e^{-}$ from valency shell ${4S}^1$ is very easily. So, the $1^{st}$ ionisation potential is very low.

$\Rightarrow$ But for removing $2^{nd}$ electron it requires more energy because ${3d}^5$ is half filled. So, it have high second ionisation potential.