Hypervalent molecule

A molecule whose Lewis structure assigns more than eight valence electrons to a central atom. Hypervalency describes electron counting in a structure, not necessarily a literal expansion of atomic orbitals.

Three-center four-electron bond: A bond in which four electrons are shared across three atoms. This model explains bonding in many hypervalent molecules, including xenon fluorides.
Lewis structure: A diagram showing atoms, bonds, and valence electrons as dots or lines. Hypervalency is defined by the electron count assigned in this representation.
Sulfur hexafluoride: A colorless gas with one sulfur atom bonded to six fluorine atoms in an octahedral arrangement. Its Lewis structure assigns twelve bonding electrons to sulfur.
Valence bond theory: A bonding theory that describes molecules through localized bonds formed by overlap of atomic orbitals. Its traditional expanded-orbital account of hypervalency contrasts with delocalized molecular-orbital explanations.
Sulfur hexafluoride as an insulator: The use of sulfur hexafluoride gas to insulate electrical equipment because of its strong dielectric properties. A familiar hypervalent molecule has major applications in high-voltage technology.
Molecular orbital theory: A theory describing bonds through molecular orbitals spread across an entire molecule. It accounts for delocalized bonding that localized Lewis structures represent imperfectly.
Valence electron: An electron in an atom's outer shell that can participate in chemical bonding. Counting these electrons around a central atom identifies a hypervalent Lewis structure.
Phosphorus pentachloride: A compound with one phosphorus atom and five chlorine atoms; its gas-phase molecule is trigonal bipyramidal. Its Lewis structure assigns ten bonding electrons to phosphorus.
Ionic bonding: Chemical bonding driven primarily by electrostatic attraction between oppositely charged ions. Highly polar bonds can make an expanded-octet Lewis picture less representative of shared electron density.
Greenhouse gas: A gas that absorbs and emits infrared radiation, contributing to atmospheric warming. Sulfur hexafluoride is an exceptionally potent greenhouse gas, linking a canonical example to climate impacts.

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