hydrideion

A hydride ion, also known as a hydride or hydrogen anion, is a negatively charged ion with the chemical formula H−. It consists of a hydrogen atom that has gained an extra electron, resulting in a species with a single proton nucleus and two electrons orbiting it.

Hydride ions are typically encountered in inorganic chemistry, particularly in metal hydrides, where they serve as the anionic component. They are largely found in compounds such as sodium hydride (NaH), calcium hydride (CaH2), and other metal hydrides, especially in solid state. These compounds are often used as reducing agents or in hydrogen storage applications.

The hydride ion is characterized by its high reactivity and strong basicity. It readily reacts with protic substances such as water or acids, generating hydrogen gas (H2). For example, when sodium hydride reacts with water, it produces sodium hydroxide and hydrogen gas:

NaH + H2O → NaOH + H2↑

In terms of electronic structure, the hydride ion has a stable noble gas configuration, similar to helium, with two electrons completing its outermost shell. Its small size and high charge density contribute to its strong tendency to donate electrons in chemical reactions.

Hydride ions are also important in various chemical synthesis processes, including hydride transfer reactions, where they serve as nucleophiles. The study of hydride chemistry is essential for understanding a wide range of inorganic and organometallic reactions.