Ionic hydrides composed of an electropositive metal, generally, an alkali or alkaline-earth metal (except beryllium and magnesium) formed by transferring of electrons from metal to hydrogen atoms. They can be prepared by the reaction of elements at about 400°C. These are salt-like, high-melting, white, crystalline solids having hydride ions (H-) and metal cations (Mn+).
2Li(s) + H2(s) → 2LiH(s) (Lithiuinhydride)
2 Ca(s) + H2(g) → 2 CaH2(g) (Calcium hydride)
