<P> In chemistry, a lone pair refers to a pair of valence electrons that are not shared with another atom and is sometimes called a non-bonding pair . Lone pairs are found in the outermost electron shell of atoms . They can be identified by using a Lewis structure . Electron pairs are therefore considered lone pairs if two electrons are paired but are not used in chemical bonding . Thus, the number of lone pair electrons plus the number of bonding electrons equals the total number of valence electrons around an atom . </P> <P> Lone pair is a concept used in valence shell electron pair repulsion theory (VSEPR theory) which explains the shapes of molecules . They are also referred to in the chemistry of Lewis acids and bases . However, not all non-bonding pairs of electrons are considered by chemists to be lone pairs . Examples are the transition metals where the non-bonding pairs do not influence molecular geometry and are said to be stereochemically inactive . </P>

Where are the lone-pair electrons on the central atom located