Lone pair

A lone pair is a pair of valence electrons associated with one atom rather than shared between atoms in a covalent bond. Its charge distribution can influence molecular shape, polarity, and reactivity.

Valence electron: An electron in an atom’s outermost shell that can participate in bonding or chemical reactions. Lone pairs consist of valence electrons that remain associated with one atom.
VSEPR theory: A model that predicts molecular geometry by treating electron domains around a central atom as mutually repelling. Lone pairs repel bonding domains and can compress bond angles.
Ammonia: A nitrogen hydride, NH₃, with a trigonal-pyramidal molecular shape. Nitrogen’s lone pair gives ammonia its pyramidal geometry and basicity.
Bonding pair: A pair of electrons shared between two atoms in a covalent bond. It is the direct counterpart to a pair localized on one atom.
Lewis structure: A diagram showing valence electrons as bonds and dots around atoms in a molecule or ion. Lewis structures represent lone pairs as dots beside their atom.
Bent's rule: A rule describing how a central atom directs its hybrid orbitals toward electropositive or electronegative substituents. Orbital character in bonds and lone pairs can shift according to the attached atoms.
Water: A compound of hydrogen and oxygen, H₂O, with a bent molecular shape. Two oxygen lone pairs help make water bent and polar.
Resonance: A representation of electron delocalization using multiple contributing Lewis structures. Resonance can spread electrons that a single Lewis structure depicts as a lone pair.
Covalent bond: A chemical bond formed when atoms share one or more pairs of electrons. A covalent bond shares an electron pair; a lone pair does not.
Nucleophile: A species that donates an electron pair to form a chemical bond with an electron-poor center. A lone pair is a common source of the electrons a nucleophile donates.

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