Match the ions given in Column I with their characteristic properties given in Column II. S.No. Column I S.No. Column II A Cr²⁺ P Stable in aqueous medium and has magnetic moment equal to 5.92 BM. B Cu^+ Q Only stable oxidation state and does not act as reducing agent. C Mn²⁺ R Is a good reducing agent due to attainment of stable d^3 configuration. D Sc³⁺ S Unstable in aqueous medium and readily disproportionates.

Step-by-step solution

For Cr ²⁺ , the electronic configuration is [Ar]3d^4 . It acts as a strong reducing agent because it gets oxidized to Cr ³⁺ ( [Ar]3d^3 ), which has a stable half-filled t_ 2g subshell in octahedral fields. Thus, A matches R. For Cu ⁺ , the electronic configuration is [Ar]3d¹⁰ . In aqueous solution, Cu ⁺ is unstable and undergoes disproportionation to Cu ²⁺ and Cu . Thus, B matches S. For Mn ²⁺ , the electronic configuration is [Ar]3d^5 . It has 5 unpaired electrons, so the magnetic moment is = n(n+2) = 5(7) = 35 5.