The oxidation state of chlorine in perchloric acid $(HClO_4)$ is:

Consider the following compounds:
$\underline{K}O_2$,$H_2\underline{O}_2$ and $H_2\underline{S}O_4$.
The oxidation states of the underlined elements in them are,respectively,

What are the oxidation states of the two sulfur atoms in thiosulfuric acid $(H_2S_2O_3)$?

The oxidation number of nitrogen in $NO_3^-$ is

An acidic solution of sodium thiosulfate is unstable because in thiosulfate,the two sulfur atoms have different oxidation states of:

When $K_2Cr_2O_7$ is converted to $K_2CrO_4$,the change in the oxidation state of chromium is