hipervalente

Hipervalente, or hypervalent, is a term in chemistry describing molecules in which a central atom bears more than eight electrons in its valence shell. This arrangement violates the classic octet rule but is common among heavier main‑group elements and is a recognized feature of hypervalent chemistry.

Common examples include PF5, SF6, IF7 and XeF4, in which the central atoms expand their valence shells to accommodate ten, twelve, fourteen or more electrons. Hypervalent species are typically found in compounds of phosphorus, sulfur, iodine and xenon, among others, and can arise in neutral molecules as well as charged ions.

Bonding descriptions vary. Early models invoked participation of low‑lying d orbitals to expand the octet, but this view is now viewed as oversimplified. Modern explanations rely on three‑center four‑electron bonds and delocalized molecular orbitals that distribute electron density over several atoms. In many cases, the observed geometries and bond properties align with both valence‑bond and molecular‑orbital pictures, and VSEPR theory can accommodate expanded octets.

Applications of hypervalence include reagents used in organic synthesis, particularly hypervalent iodine compounds such as Dess‑Martin periodinane and iodobenzene diacetate (IBX). These reagents are valued for mild oxidation, rearrangements and functional group transformations, making hypervalent species important tools in synthetic chemistry.

See also: octet rule, three‑center four‑electron bonding, VSEPR theory.