Lone pair

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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.