$A$ metal ion $M^{3+}$ after the loss of three electrons in a reaction will have an oxidation number equal to

In which of the following,oxygen has $+2$ oxidation number?

Find out the oxidation number of chlorine in the following compounds and arrange them in increasing order of oxidation number of chlorine.
$NaClO_4, NaClO_3, NaClO, KClO_2, Cl_2O_7, ClO_3, Cl_2O, NaCl, Cl_2, ClO_2$.
Which oxidation state is not present in any of the above compounds?

Arrange $ICl$,$HI$,$I_2$,and $HIO_4$ in the decreasing order of the oxidation number of iodine.

Consider the following molecules: $Br_3O_8$,$F_2O$,$H_2S_4O_6$,$H_2S_5O_6$,and $C_3O_2$. Count the number of atoms existing in their zero oxidation state in each molecule. Their sum is . . . . .

The oxidation states of sulphur in the anions $SO_3^{2-}$,$S_2O_4^{2-}$ and $S_2O_6^{2-}$ follow the order: