A specific divalent cation () in the transition series causes a sharp break in the linearly increasi — d and f Block Elements Chemistry Question

💡 Solution & Explanation

The element is Manganese ($Mn$). Its second ionization leaves the highly stable $Mn^{2+}$ ion with an exactly half-filled $3d^5$ configuration. Removing a third electron to form $Mn^{3+}$ requires breaking this stability, resulting in an unusually high third ionization enthalpy. The $3d^5$ configuration possesses exactly $5$ unpaired electrons.