The oxidation number of $Ba$ in barium peroxide is

What are the oxidation numbers of sulfur in $S_8$,$S_2F_2$,and $H_2S$ respectively?

If a metal ion $M^{3+}$ loses three more electrons,what will be its final oxidation number?

What are the oxidation states of the most electronegative element in the products of the reaction between $BaO_2$ and $H_2SO_4$?

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 . . . . .

What is the oxidation number of $Fe$ in $Fe_3O_4$?