lone pair
Noun
Meaning
lone pair (plural lone pairs)
(chemistry) A pair of electrons in the valence shell of an atom that does not participate in bonding.
Examples
We may say that a basic substance is one which has a lone pair of electrons which may be used to complete the stable group of another atom, and that an acid is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms.
Chirality main Amines of the type NHRR′ and NRR′R″ are chiral : the nitrogen atom bears four substituents counting the lone pair.
Figure 1: Dehydration synthesis (condensation) reaction forming an amide Cis/trans isomers of the peptide group Significant delocalisation of the lone pair of electrons on the nitrogen atom gives the group a partial double bond character.
As a result, the lone pair does not contribute to the aromatic system but importantly influences the chemical properties of pyridine, as it easily supports bond formation via an electrophilic attack.
One lone pair is used as a sigma X donor, the other two lone pairs are available as L-type pi donors.
For example, hydrogen fluoride—which has three lone pairs on the F atom but only one H atom—can form only two bonds; ( ammonia has the opposite problem: three hydrogen atoms but only one lone pair).