In chemistry, a hydride is the anion of hydrogen, H−, or a compound in which one or more hydrogen centers have nucleophilic, reducing, or basic properties. In compounds that are regarded as hydrides, hydrogen is bonded to a more electropositive element or group. Compounds containing metal or metalloid bonds to hydrogen are often referred to as hydrides, even though these hydrogen centers can have a protic character.
Hydrides may refer to any compound that hydrogen forms with other elements  , ranging over most of the periodic table, groups 1–16. This historic meaning is dealt with only in terms of formal nomenclature at the end of the article, the rest of the article concerns the popular meaning.
Bonds between hydrogen and other elements range from highly covalent to somewhat ionic. Hydride compounds often do not conform to classical electron-counting rules, but are described as well as multi-centered bonds and metallic bonding. Hydrides can be components of discrete molecules, oligomers or polymers, ionic solids, chemisorped monolayers, bulk metals (interstitial), and other materials. While hydrides traditionally react as Lewis bases or reducing agents, some metal hydrides behave as hydrogen-atom donors and as acids.
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