Lewis Diagrams

Lewis diagrams, also known as Lewis dot structures, are visual representations of the valence electrons in atoms, and how they interact in chemical bonds.
They use dots and lines to represent electrons. Dots are used for non-bonding or lone pair electrons, and lines are used for bonding electrons.
The structure of a Lewis diagram emphasises the octet rule, where atoms tend to gain, lose, or share electrons to achieve a stable configuration of eight electrons in their outermost layer.

Drawing Lewis Diagrams

Begin by determining the total number of valence electrons for all the atoms in the molecule or compound. Typically, this total should reflect the octet rule.
The least electronegative atom is often placed at the centre and the other atoms arranged around it.
Connect each outer atom to the central atom with a single line, representing a covalent bond. This means two electrons are shared between the two atoms.
Fill the valence shells of the outer atoms before the central one. Remember, Hydrogen only needs two electrons rather than eight.
Where possible, atoms share electrons to form multiple covalent bonds, shown as double or triple lines in the Lewis diagram, until all atoms meet the octet rule.

They do not show the three-dimensional structure of molecules.
They are less effective for showing the structure of molecules with elements that exceed the octet rule.
Lewis diagrams also do not provide information on bond energies or lengths, and sometimes have difficulty accurately depicting molecules with complex delocalised electron systems, like those found in aromatic compounds.