Xenon difluoride

Xenon difluoride (XeF₂) is a colorless crystalline compound of xenon and fluorine. It acts as a fluorinating agent and selectively etches silicon.

Three-center four-electron bond: A molecular bond in which four electrons are shared across three atoms, often producing a linear arrangement. XeF₂’s linear F–Xe–F unit is a classic example of this bonding model.
Silicon etching: The removal of silicon from a surface through chemical or physical processes. XeF₂ enables selective removal of exposed silicon in microfabrication.
Neil Bartlett: A British chemist whose 1962 synthesis of xenon hexafluoroplatinate demonstrated noble-gas compound formation. Bartlett’s result prompted attempts to prepare xenon fluorides, including XeF₂.
Xenon: A colorless, odorless noble gas with atomic number 54. Xenon is the central atom in XeF₂ and supplies the unusual heavy-atom chemistry.
VSEPR theory: A model that predicts molecular shapes by treating electron domains around a central atom as mutually repelling. It accounts for XeF₂’s linear shape from three lone pairs and two bonding domains.
Xenon difluoride etching: A dry etching process in which xenon difluoride gas reacts with silicon to form volatile products. This is the compound’s distinctive use in releasing silicon structures and creating cavities.
Noble gas compounds: Chemical compounds containing elements from Group 18, once thought unable to form ordinary chemical bonds. XeF₂ belongs to the class whose existence reshaped ideas about noble-gas inertness.
Fluorine: A highly reactive halogen with atomic number 9 and the greatest electronegativity of any element. Fluorine forms the two Xe–F bonds and drives the compound’s fluorinating behavior.
Molecular orbital theory: A theory describing electrons as occupying orbitals distributed across an entire molecule. It gives a fuller account of the delocalized bonding in XeF₂ than a simple Lewis structure.
Microelectromechanical systems: Miniaturized devices that combine mechanical and electrical components, often fabricated on silicon wafers. XeF₂ etching can undercut silicon and free suspended MEMS components.

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