L

Lone Pair

Quick Reference
Also Known AsNon-bonding pair, unshared electron pair, non-bonding electrons

What is Lone Pair?

A pair of valence electrons not involved in bonding, residing on a single atom. Lone pairs occupy more space than bonding pairs and repel bonding pairs more strongly, distorting molecular geometry. They are important in Lewis base character, hydrogen bonding, and coordination chemistry.

Properties & Characteristics

A lone pair (non-bonding pair) is a pair of valence electrons on an atom that is not shared with another atom in a covalent bond. In Lewis structures, lone pairs are shown as pairs of dots on the atom. Lone pairs are electrostatically repulsive (repel bonding pairs), influencing molecular geometry (VSEPR): water has 2 lone pairs on O, making it bent; ammonia has 1 lone pair on N, making it pyramidal. Lone pairs can donate to Lewis acids (making the atom a Lewis base or nucleophile).

Uses & Applications

Lone pair chemistry is central to: Lewis base-acid reactions (lone pair donated to Lewis acid), Brønsted base behaviour (lone pair on N accepts H⁺), nucleophilicity in organic reactions (lone pair on O, N, S, halide attacks electrophile), and coordination chemistry (ligand lone pairs bond to metal centres).

Safety Information

Atoms with lone pairs (O, N, S) are often responsible for the toxicity of chemical compounds: sulfhydryl groups (-SH) coordinate to toxic heavy metals, amine groups bind to reactive carcinogens, oxygen lone pairs activate peroxides. Understanding lone pair reactivity helps predict toxic mechanisms.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Lone Pair
Synonyms Non-bonding pair, unshared electron pair, non-bonding electrons

Frequently Asked Questions

A pair of valence electrons not involved in bonding, residing on a single atom. Lone pairs occupy more space than bonding pairs and repel bonding pairs more strongly, distorting molecular geometry. They are important in Lewis base character, hydrogen bonding, and coordination chemistry.

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