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

`V (Z = 23): 1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(2)`
`Cr (Z = 24): 1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(5)4s^(1)`
`Mn (Z = 25): 1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(5)4s^(2)`
`Fe (Z = 26): 1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(5)4s^(2)`
Since it is relatively difficult to remove an electron form the extra stable half-filled subshell `(3d^(5)),Mn` has the highest third ionization enthalphy:
`Mn(326kJ mol^(-1)) gt Cr (2990) gt Fe (2962) gt V (2833)`