Question

Which of the following has highest second ionization energy?

• A. Ni
• B. V
• C. Cr
• D. Mn

Answer 1

Answer: (C)

Electronic configuration for chromium is :
${}_{24}Cr\to 1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{5}4s^1$
After ionisation of $4s$ electron the next electron which will be ionised is from $3d$ orbital. As $3d^5$ electronic configuration, is stable, hence, the second ionisation of $Cr$ will require much greater ionisation energy than the expected one.