Which one of the following species is not capablc of showing dispropor* tionation reaction ?

A disproportionation reaction occurs when an element in a single oxidation state is simultaneously oxidized and reduced. For this to happen, the element must exist in an intermediate oxidation state, allowing it to both increase and decrease its oxidation number. In the oxyanions of chlorine, the oxidation states are +1 for ClO⁻, +3 for ClO₂⁻, +5 for ClO₃⁻, and +7 for ClO₄⁻. The perchlorate ion (ClO₄⁻) contains chlorine in its maximum possible oxidation state of +7 [1]. Since chlorine cannot be further oxidized beyond +7, it cannot undergo disproportionation. In contrast, ClO⁻, ClO₂⁻, and ClO₃⁻ can all undergo such reactions because their chlorine atoms are in intermediate states (+1, +3, and +5) and can move to both higher and lower oxidation levels [1].

Sources

1. [1] https://downloads.regulations.gov/EPA-HQ-OPP-2005-0507-0012/content.pdf