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.