Abnormal electronic configurations are observed in which pair?A.Cu, CrB.Pd, PtC.Cr, NiD.Both A and B

Abnormal electronic configurations are typically observed in transition metals, where the energy difference between the ns and (n-1)d orbitals is small. This can lead to exceptions to the usual electron filling order. Among the given options, both copper (Cu) and chromium (Cr) exhibit abnormal electronic configurations:

A. Copper (Cu) - It has an abnormal electronic configuration in its ground state, where one electron is promoted from the 4s orbital to the 3d orbital, resulting in a filled 3d orbital and a half-filled 4s orbital.

C. Chromium (Cr) - Similarly, chromium has an abnormal electronic configuration in its ground state, with one electron promoted from the 4s orbital to the 3d orbital, resulting in a half-filled 3d orbital and a singly occupied 4s orbital.

So, the correct answer is D. Both A and C.