The oxidation number of $P$ in $Mg_3(PO_4)_2$ is ........

What is the oxidation number of $Cr$ in $K_{2}Cr_{2}O_{7}$?

In the reaction of potassium dichromate,potassium chloride and sulfuric acid (conc.),the oxidation state of the chromium in the product is $(+)$ . . . . . . .

The oxidation state of sulfur in the anions $SO_3^{2-}$,$S_2O_4^{2-}$,and $S_2O_6^{2-}$ increases in the order:

Assertion: In some cases,oxygen exhibits a positive oxidation state. Consequently,it is an electronegative element.
Reason: Fluorine is more electronegative than oxygen.

$1 \ mol$ of compound $N_2H_4$ loses $10 \ mol$ of electrons to form a new compound $Y$. Assuming all nitrogen atoms are present in compound $Y$,what is the oxidation state of $N$ in compound $Y$?