What is the formula of the manganate ion?

$2.5 \ mol$ of hydrazine $(N_2H_4)$ loses $25 \ mol$ of electrons to form a new compound $X$. Assuming all lost electrons are contained in the new compound,what is the oxidation state of nitrogen in compound $X$?

The oxidation number of $C$ in $HNC$ is:

What is the oxidation state of phosphorus in the phosphate ion $(PO_4^{3-})$?

In ferrous ammonium sulphate,the oxidation number of $Fe$ is:

In chromite ore,the oxidation number of iron and chromium are respectively