Which chlorine species can act as an oxidizing agent but not as a reducing agent?


> 
> Which species can act as an oxidizing agent but not as a
>  reducing agent?
> 
> 
> (A) $\ce{Cl2}$  
> 
>  (B) $\ce{Cl-}$  
> 
>  (C) $\ce{ClO2-}$  
> 
>  (D) $\ce{ClO4-}$ 
> 
> 
> 


I thought the answer was A because if $\ce{Cl}$ is reduced, it becomes very stable with a full octet and therefore cannot be the reducing agent; however, according to the 2007 Chemistry Olympiad answer key, the answer is D. Why is that?




For a species to act as a reducing agent, it should have the ability to get oxidised. Any element in its highest oxidation state, cannot oxidise anymore, and can hence not act as a reducing agent. $\ce{ClO4-}$ has $\ce{Cl}$ in $+7$ oxidation state, and cannot have a higher oxidation state, and hence cannot act as a reducing agent.


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