Regarding the ionization enthalpies (IE) of transition elements, which of the following statements a — d and f Block Elements Chemistry Question

💡 Solution & Explanation

(A) is correct; added $d$ -electrons effectively shield the outer $s$ -electrons, making the IE rise slower than in p-block elements. (B) is incorrect because $Fe^{3+}$ is $3d^5$; the third IE of Iron removes an electron from $Fe^{2+}$ ($3d^6$), which is relatively easy (yielding stable $3d^5$), breaking the steady increase trend. The break occurs at $Mn^{2+}$ (removing from $3d^5$) and $Fe^{3+}$ (removing from $3d^5$ would be the 4th IE). (C) is incorrect; $5d$ IEs are higher than $4d$ due to poor $4f$ shielding. (D) is correct; $Zn$ has maximum first IE in $3d$ due to $s^2 d^{10}$ stability.