The first, second, and third ionisation enthalpies ( _i H₁, _i H₂ , and _i H₃ ) for four consecutive 3 d transition metals (labelled A, B, C, and D) are given in the table below (in kJ~mol ⁻¹ ): Element _i H₁ _i H₂ _i H₃ A 653 1592 2987 B 717 1509 3248 C 762 1561 2957 D 758 1646 3232 Identify the transition metal corresponding to element B.

Step-by-step solution

The table shows successive ionisation enthalpies. Element B has a relatively normal first and second ionisation enthalpy, but its third ionisation enthalpy ( _i H₃ = 3248 ~kJ~mol ⁻¹ ) is exceptionally high compared to element C ( _i H₃ = 2957 ~kJ~mol ⁻¹ ). This indicates that the removal of the third electron from element B is very difficult, which happens when the +2 ion has a stable half-filled or fully-filled configuration. Manganese ( Mn ) has the electronic configuration [ Ar ] 3 d ^5 4 s ^2 . Its +2 ion, Mn ²