The transition metal having highest 3 rd ionisation enthalpy is:

Step-by-step solution

Ionization energy, in chemistry and physics, the amount of energy required to remove an electron from an isolated atom or molecule. 3 rd Ionisation energy: V : 2833 kJ / mol Cr : 2990 kJ / mol Mn : 3260 kJ / mol Fe : 2962 kJ / mol alternative Mn : 3 d 5 4 s 2 Fe : 3 d 6 4 s 2 Cr : 3 d 5 4 s 1 V : 3 d 3 4 s 2 So Mn has highest 3 rd IE among all the given elements due to d 5 configuration