Electride

An ionic compound in which some electrons serve as anions, occupying sites normally held by negatively charged atoms or groups. Its unusual electron-rich structure can produce distinctive electrical, optical, and chemical properties.

Anionic electron: An electron that occupies an anion-like site in a material rather than belonging to an ordinary atom or molecule. This is the defining charge-bearing unit in an electride.
Ionic compound: A substance whose structure is held together substantially by electrostatic attraction between oppositely charged ions. Electrides extend ionic bonding by allowing electrons themselves to supply negative charge.
William L. Jolly: An American inorganic chemist known for research on unusual oxidation states and alkali-metal compounds. His work helped establish the chemistry of compounds with electron-rich anionic behavior.
Low-work-function material: A material from which electrons can be emitted or removed with relatively little energy. Electrides can release electrons readily, making them candidates for electron-emitting surfaces.
Solvated electron: An electron stabilized by surrounding solvent molecules rather than bound to a particular atom. Both are unusually mobile or weakly bound electrons, but an electride embeds them in a solid structure.
Interstitial electron: An electron localized in a space between atoms in a solid. Many crystalline electrides place their anionic electrons in interstitial spaces.
Crystal structure: The ordered, repeating arrangement of atoms, ions, or molecules in a crystalline solid. Its cavities and channels determine where an electride can host anionic electrons.
James L. Dye: An American chemist who studied solvated electrons, alkalides, and electrides. His investigations of alkali-metal solutions and complexes shaped the modern electride concept.
Electron emission: The release of electrons from a material into a surrounding vacuum or medium. The weakly bound electrons of some electrides can support efficient emission.
Metal: A material with metallic bonding, typically characterized by mobile electrons and high electrical conductivity. Conducting electrides can resemble metals, yet their electrons occupy anion-like structural sites.

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Disodium helideNarrower topic: Na₂He belongs to this class because its localized electrons occupy lattice cavities.