Which of the following arrangements represent increaseing oxidation number of the central atom?

Options

A. `CrO_(2)^(-),ClO_(3)^(-),CrO_(4)^(2-),MnO_(4)^(-)`
B. `CrO_(3)^(-),CrO_(4)^(2-), MnO_(4)^(-),CrO_(2)^(-)`
C. `CrO_(2)^(-),ClO_(3)^(-), MnO_(4)^(-),CrO_(4)^(2-)`
D. `CrO_(4)^(2-), MnO_(4)^(-),CrO_(2)^(-),ClO_(3)^(-)`

Answer

A

Explanation

Writing the oxidation number (O.N.) of Cr, Cl and Mn on each species in the four set of ions then,
(a) `overset(+5)(CrO_2^(-)),overset(+5)(ClO_3^(-)),overset(+6)(CrO_4^(2-)),overset(+7)(MnO_(4)^(-))`
(b) `overset(+5)(ClO_3^(-)),overset(+6)(CrO_4^(2-)),overset(+7)(MnO_(4)^(-)),overset(+3)(CrO_2^(-))`
(c) `overset(+3)(CrO_(2)^(-)),overset(+5)(ClO_3^(-)),overset(+7)(MnO_4^(-)),overset(+6)(CrO_4^(2-))`
(d) `overset(+6)(CrO_4^(2-)),overset(+7)(MnO_4^(-)),overset(+3)(CrO_(2)^(-)),overset(+5)(ClO_3^(-))`
Only in the arrangement (a), the O.N. of central atom increases form left to right, therefore, option (a) is correct.