Chlorine can be found as the following oxoanions $\ce{ClO–} , \ce{ClO2-}, \ce{ClO3-}, \ce{ClO4-}$ in many chemical stockrooms. However, iodine is never found as $\ce{IO4-}$. Explain this observation.
I didn't really find any reason as to why periodate cannot exist, unlike anions such as flourate where it is limited by flourine's small size. After researching this further, I found that the periodate anion actually exists in compounds such as sodium periodate. Even though it has another form $\ce{IO6^{5-}},$ the periodate anion actually dominates its equilibrium. Thus, I was wondering what the intended/likely answer was?