Water ${\text{(H}}_{\text{2}}\text{O)}$ is formed by the reaction of hydrogen ${\text{(}}_1^1\text{H)}$ with all isotopes of Oxygen i.e ${ }^{16}{\text{O, }}^{17}\text{O}$ and ${ }^{18}\text{O}$.  In which case the percentage of hydrogen (H) is maximum in water.