In
chemistry, an
unpaired electron is an
electron that occupies an
orbital of an
atom singly, rather than as part of an
electron pair. As the formation of electron pairs is often energetically favourable, either in the form of a
chemical bond or as a
lone pair, unpaired electrons are relatively uncommon in chemistry, because an entity that carries an unpaired electron is usually rather reactive. In
organic chemistry they typically only occur briefly during a reaction on an entity called a
radical; however, they play an important role in explaining reaction pathways.