Ion X is a divalent cation ( M ²⁺ ) of the 3 d transition series that acts as a strong reducing agent in aqueous solution and has a spin-only magnetic moment of 4.90 BM . Ion Y is a trivalent cation ( M ³⁺ ) of the same series that acts as a strong oxidizing agent in aqueous solution and also has a spin-only magnetic moment of 4.90 BM . Identify the ions X and Y respectively.

Step-by-step solution

The spin-only magnetic moment is given by = n(n+2) BM . For = 4.90 BM , the number of unpaired electrons n = 4 . For a divalent ion ( M ²⁺ ) in the 3 d series, n=4 corresponds to either 3 d ⁴ ( Cr ²⁺ ) or 3 d ⁶ ( Fe ²⁺ ). Ion X is a strong reducing agent, meaning it readily oxidizes to a more stable state. Cr ²⁺ ( 3 d ⁴ ) oxidizes to Cr ³⁺ ( 3 d ³ ), which is highly stable in aqueous solution due to a half-filled t_ 2g level. Thus, X is Cr ²⁺ . For a trivalent ion ( M ³⁺ ), n=4 corresponds to either 3 d ⁴ ( Mn ³⁺ )