Let x be the maximum number of identical Cr - O bonds in the chromate ion ( CrO ₄²⁻ ), and y be the maximum number of identical Cr - O bonds in the dichromate ion ( Cr ₂ O ₇²⁻ ). The value of (x + y) is:

Step-by-step solution

In the chromate ion ( CrO ₄²⁻ ), resonance occurs among all four oxygen atoms. As a result, all four Cr - O bonds are identical in length. Thus, the maximum number of identical Cr - O bonds is x = 4 . In the dichromate ion ( Cr ₂ O ₇²⁻ ), the structure consists of two CrO ₄ tetrahedra sharing one oxygen atom ( O ₃ Cr - O - CrO ₃ ). Resonance occurs independently within the two terminal CrO ₃ groups. Therefore, the six terminal Cr - O bonds are identical to each other. The two bridging Cr - O bonds are longer and no