, a Lewis structure
is a 2D representation of a molecule
on paper. It is used primarily to show the approximate relative positions of each atom
in relation to the other atoms in the molecule, the topology
of the covalent bonds
linking them, and the allocation of electrons
to the atoms in the molecule.
A number of heuristic rules (based mostly on the octet rule) can then be applied to work out the distribution of charge across the structure. This does not always produce correct results, but works in enough cases to make Lewis structures a useful tool in chemistry.
It was devised and named after G. N. Lewis.