Out of the two allotropic forms of dihydrogen,the form with lesser molecular energy is

Arrange the following:
$(i)$ $CaH_{2}$,$BeH_{2}$,and $TiH_{2}$ in order of increasing electrical conductance.
$(ii)$ $LiH$,$NaH$,and $CsH$ in order of increasing ionic character.
$(iii)$ $H-H$,$D-D$,and $F-F$ in order of increasing bond dissociation enthalpy.
$(iv)$ $NaH$,$MgH_{2}$,and $H_{2}O$ in order of increasing reducing property.

Which of the following orders is incorrect?

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

Explain the isotopes of hydrogen in short.

Which of the following pairs will not produce $H_2$ gas?