Question

The atomic numbers of vanadium, chromium, manganese and iron are respectively $23,24,25,26$. Which one of these may be expected to have the highest second ionisation energy?

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

Answer 1

Answer: (B)

$Cr$

The atomic numbers of vanadium, chromium, manganese, and iron are respectively 23, 24, 25, 26. Chromium may be expected to have the highest second ionisation energy.

The electronic configuration of chromium is $\left[Ar\right]3d^{5}4s^1$
It loses one electron to form $\left[Ar\right]3d^{5}4s^0$ in which 3d subshell is half-filled and stable. When another electron is removed, it is removed from half-filled 3d subshell and the stability of 3d subshell is lost. This requires higher energy.