Which of the following statement$(s)$ is/are correct:
$A$. $NaH$ is a non-volatile hydride
$B$. $MgH_2$ is a polymeric hydride
$C$. $NH_3$ is an electron-precise hydride
$D$. $H_2O$ is an electron-rich hydride

Saline hydrides are known to react with water violently producing fire. Can $CO_2$,a well-known fire extinguisher,be used in this case? Explain.

The correct statements among $(a)$ to $(d)$ are:
$(a)$ Saline hydrides produce $H_2$ gas when reacted with $H_2O$.
$(b)$ Reaction of $LiAlH_4$ with $BF_3$ leads to $B_2H_6$.
$(c)$ $PH_3$ and $CH_4$ are electron-rich and electron-precise hydrides,respectively.
$(d)$ $HF$ and $CH_4$ are called as molecular hydrides.

Under what conditions can hydrogen behave as a metal?

State the abundance and symbol of protium and deuterium in hydrogen atoms.

Number of nucleons in $D_2$ molecule is