What is the oxidation number of $S$ in $SO_3^{2-}$?

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?

One mole of $N_2H_4$ loses $10 \ moles$ of electrons to form a new compound $Z$. Assuming that all the nitrogen atoms appear in the new compound,what is the oxidation state of nitrogen in $Z$? (There is no change in the oxidation state of hydrogen.)

The oxidation number of nitrogen in $NH_2OH$ is

What is the oxidation number of fluorine in $F_2O$?

What is the oxidation number of sulfur in $Na_2S_4O_6$?