KCET 2025 Chemistry Paper

To determine which pairs of elements do not both have the configuration (n−1)d10ns2, let's examine the electronic configurations provided:
Cu (Copper): [Ar]3d104s1
Zn (Zinc): [Ar]3d104s2
Cd (Cadmium): [Kr]4d105s2
Hg (Mercury): [Xe]4f145d106s2
Ag (Silver): [Kr]4d105s1
From the configurations:
Copper (Cu) does not have an ns2 configuration (as it is 4s1 ).
Silver (Ag) also lacks an ns2 configuration (as it is 5s1 ).
Thus, in the pair consisting of Ag and Cu, neither element has the (n−1)d10ns2 configuration.