What is the oxidation number of $Xe$ in $Ba_2XeO_6$?

Oxidation numbers of $P$ in $PO_4^{3-}$,of $S$ in $SO_4^{2-}$ and that of $Cr$ in $Cr_2O_7^{2-}$ are respectively

What is the oxidation number of $Mn$ in $MnO_4^{-}$?

What is the oxidation number of $As$ in $H_{3}AsO_{3}$?

What is the oxidation state of chlorine in chlorous acid?

State whether the following statements are True or False:
$(1)$ The oxidation number of nitrogen in ammonium chloride $(NH_4Cl)$ is $(-3)$.
$(2)$ The oxidation number of $C$ in methyl chloride $(CH_3Cl)$ is $(-2)$.
$(3)$ In the following reaction,the oxidation number of $Br$ changes from $0$ to $+5$: $Br_2 \to BrO_3^-$.