Four successive members of the first row transition elements are listed below with their atomic number. Which one of them is expected to have the highest third ionisation enthalpy ?

Options

A. vanadium (Z=23)
B. chromium (Z=24)
C. iron (Z=26)
D. maganese (Z=25)

Answer

D

Explanation

(A) V(Z=23): `1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(2)3d^(3)`
(B) Cr(Z=24): `1s^(2)2s^(2)2p^(6)3s^(2)4s^(2)3d^(6)`
(C) Fe (Z=26) : `1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(2)3d^(6)`
(D) Mn(Z=25) : `1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(2)3d^(4)`
third ionisation energy will be highest in case of Mn(Z=25) as the third electron has to be removed from exactly half filled 3d -subshell