How do ionic hydrides differ from covalent hydrides?

Ionic (or saline) hydrides and covalent hydrides differ primarily in their chemical bonding, composition, and reactivity.

Ionic Hydrides

• Composition: These are typically formed by alkali metals and alkaline-earth metals.1
• Bonding: They contain hydrogen as a negatively charged ion, $H^{-}$, which acts as a strong base.1
• Properties: They are generally white crystalline solids that react vigorously with water to produce hydrogen gas. Because of this reactivity, they are often used as portable sources of hydrogen.1

Covalent Hydrides

• Composition: These are primarily compounds of hydrogen and [nonmetals].2
• Bonding: The bonds consist of electron pairs shared between atoms of comparable electronegativity.2
• Properties: Most are volatile gases or liquids with low melting and boiling points, though some properties are modified by hydrogen bonding. Unlike ionic hydrides, which are hydride ($H^{-}$) donors, covalent hydrides become increasingly acidic—or more likely to donate a hydrogen ion ($H^{+}$)—as one moves across the periodic table from group 13 to group 17.2