Lewis structures, also called electron-dot structures or electron-dot diagrams, are diagrams that show the bonding between atoms of a molecule, and the lone pairs of electrons that may exist in the molecule. A Lewis structure can be drawn for any covalently-bonded molecule, as well as coordination compounds. Lewis structures show each atom in the structure of the molecule using its chemical symbol. Lines are drawn between atoms that are bonded to one another (rarely, pairs of dots are used instead of lines). Excess electrons that form lone pairs are represented as pair of dots, and are placed next to the atoms on which they reside. The Lewis structure for an individual atom is drawn by placing a dot around the atom for each valence electron available. There are four positions available for dots to be placed; most chemists draw them on the top, left, bottom, and right of the atom.