Chemistry - GENERAL CHEMISTRY Question with Solution | TestHub

Identification of X and Y: X is Chromium ($Cr$, $Z=24$) because it has the maximum number of unpaired electrons ($3d^{5}4s^1$, total 6) in the 3d series, and Y is Manganese ($Mn$, $Z=25$), which is adjacent to $Cr$ and forms the tetrahedral monobasic oxyacid $HMn{O}_4$.

Analysis of Option (B): In their ground states, both $Cr$ ($3d^{5}4s^1$) and $Mn$ ($3d^{5}4s^2$) have exactly 5 electrons in their "d" subshell.

Conclusion: Since both elements have the same number of d-electrons with parallel spins, they have an equal number of exchange pairs ($\frac{5\times 4}{2}=10$) in the d-subshell, making statement (B) incorrect.