What is the sum of neutrons and protons in the heaviest isotope of hydrogen?

Hydrogen forms a stable diatomic molecule like which elements?

The product$(s)$ of the reaction $NaBH_4 + I_2 \longrightarrow$ 'Products' is/are

$B_2H_6 + 2NaH \to$ compound $P$. Identify the hybridisation of Boron in compound $P$.

Fill in the blanks:
$(1)$ In the crystal structure of ice, the oxygen atom is at a distance of $276 \ pm$ from four hydrogen atoms.
$(2)$ The relative proportion of tritium to protium is $1: 10^{18}$.

Select the correct statement regarding interstitial hydrides.