The oxidation state of each oxygen atom in $Na_{2}O_{2}$ is

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

The oxidation number of carbon in $CH_3Cl$ is:

$LiCoO_2$ crystallizes in a rhombohedral structure. Consider a situation where $50\%$ lithium $(Li)$ is extracted from the lattice. To keep the crystal electrically neutral,the change in the average oxidation state of $Co$ is

Oxidation number of $P$ in $Mg_2P_2O_7$ is

Oxidation number of $As$ atoms in $H_3AsO_4$ is