Question

Oxidation state of oxygen is 2
Here, why the oxidation state
of oxygen is -1/2?

Answer 1

In most of the compounds, the oxidation state of oxygen is always - 2.

For example : In $\sf{CO_2}$, this oxidation state of oxygen is - 2.

But in some compounds, the oxidation state of oxygen is - 1 and sometimes - 1 / 2. This is because of the presence of peroxide and superoxide.

Peroxide = $\sf{O_2^{2-}}$, in this compound, each oxygen carries - 1 charge.

For example : $\sf{H_2O_2}$

Superoxide = $\sf{O_2^-}$, in this compound, each oxygen carries - 1 / 2 charge.

For example : $\sf{KO_2}$