Question

Oxidation means _________ (gain/loss) of $O_2$ and reduction means gain of hydrogen.

Answer 1

Oxidation means a gain of $O_2$ and Reduction means gain of Hydrogen.

For example:

Oxidation: $2M{g}_{\left(s\right)}+{O_2}_{\left(g\right)}⟶2Mg{O}_{\left(s\right)}$

Reduction: ${B{r}_2}_{\left(g\right)}+H_2{S}_{\left(g\right)}⟶2HB{r}_{\left(g\right)}+S_{\left(s\right)}$

So, the correct answer is to gain.