Isotope$(s)$ of hydrogen which emits low energy $\beta^{-}$ particle with $t_{1/2}$ value $> 12 \ years$ is/are :

Identify the correct statements from the following.
$(i)$ $Zn$ reacts with dilute $HCl$ and aqueous $NaOH$ solution separately and liberates hydrogen.
$(ii)$ $Ti$ and $Zr$ form interstitial hydrides.
$(iii)$ The viscosity of $H_2 O$ is more than the viscosity of $D_2 O$.

Choose the incorrect statement for deuterium.

Which of the following facts are the evidence for the ionic nature of $LiH$?

Hydrogen combines with other elements by

Which is the lightest gas?