A lone pair is an electron pair without bonding or sharing with other atoms. They are found in the outermost electron shell of an atom, so lone pairs are a subset of a molecule's valence electrons. They can be identified by examining the outermost energy level of an electron--lone electron pairs consist of paired electrons as opposed to single electrons, which may appear if the atomic orbital is not full. Electron pairs are therefore considered lone pairs if two electrons are paired but are not used in bonding. Thus, the number of lone electrons plus the number of bonding electrons equal the total number of valence electrons from a compound. The pairs often exhibit a negative polar character with their high charge density. They are also used in the formation of a dative bond. For example, the creation of the hydronium (H₃O⁺) ion occurs when acids are dissolved in water and is due to the oxygen atom donating a lone pair to the hydrogen ion. The Electron is a fundamental subatomic particle that carries an electric charge. ... Properties In chemistry and physics, an atom (Greek ἄτομος or átomos meaning indivisible) is the smallest particle of a chemical element that retains its chemical properties. ... Example of a sodium electron shell model An electron shell, also known as a main energy level, is a group of atomic orbitals with the same value of the principal quantum number n. ... In chemistry, a molecule is an aggregate of at least two atoms in a definite arrangement held together by special forces. ... In chemistry, valence electrons are the electrons contained in the valence shell of an atom, and are likely to participate in a chemical reaction through bonding with other atoms or molecules. ... A quantum mechanical system can only be in certain states, so that only certain energy levels are possible. ... In chemistry, an atomic orbital is the region in which an electron may be found around a single atom. ... In chemistry, valence electrons are the electrons contained in the valence shell (the outermost electron level) of an atom, and which are likely to participate in a chemical reaction through bonding with other atoms, molecules, or ions. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interactions. ... A coordinate covalent bond (also known as dative covalent bond) is a special type of covalent bond in which the shared electrons come from one of the atoms only. ... In chemistry, hydronium is the common name for the cation H3O+ derived from protonation of water. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ...

An example of a lone pair on NH₃ (Ammonia)

Image File history File links Lonepair. ... Image File history File links Lonepair. ...

See also

• Ligand
• Complex (chemistry)
• Highest occupied molecular orbital