Write a short note on Ionic or Saline Hydrides.

(N/A) These are stoichiometric compounds of dihydrogen formed with most of the $s$-block elements which are highly electropositive in character. Examples include $LiH$,$BeH_{2}$,and $MgH_{2}$.
In fact,$BeH_{2}$ and $MgH_{2}$ are polymeric in structure.
The ionic hydrides are crystalline,non-volatile,and non-conducting in the solid state. However,their melts conduct electricity,and on electrolysis,they liberate dihydrogen gas at the anode,which confirms the existence of the $H^{-}$ ion.
$2 H^{-}(\text{melt}) \xrightarrow{\text{anode}} H_{2}(g) + 2 e^{-}$
Saline hydrides react violently with water,producing dihydrogen gas.
$NaH(s) + H_{2}O(l) \longrightarrow NaOH(aq) + H_{2}(g)$
Lithium hydride is relatively unreactive at moderate temperatures with $O_{2}$ or $Cl_{2}$. It is,therefore,used in the synthesis of other useful hydrides,for example:
$8 LiH + Al_{2}Cl_{6} \longrightarrow 2 LiAlH_{4} + 6 LiCl$
$2 LiH + B_{2}H_{6} \longrightarrow 2 LiBH_{4}$