Question

The atomic numbers of vanadium (V), chromium (Cr), manganese (Mn) and iron (Fe) are respectively 23, 24, 25 and 26. Which one of these may be expected to have the highest second ionisation enthalpy?

(a) V 

(b) Cr

(c) Mn 

(d) Fe.

Answer 1

(b) : The second ionisation potential values of Cu and Cr are sufficiently higher than those of neighbouring elements. This is because of the electronic configuration of Cu⁺ which is 3d¹⁰ (completely filled) and of Cr⁺ which is 3d⁵ (half-filled), i.e., for the second ionisation potentials, the electron is to be removed from very stable configurations.