Lewis Structures

Lewis dot diagrams were first used by Gilbert Newton Lewis in 1902 to represent valence electron arrangements in covalently bonded molecules.

There are two parts to a Lewis dot diagram:

1. A chemical symbol - representing all the subatomic particles in the nucleus of the atom, plus all the electrons that are NOT in the outer energy level.
    
2. One or more dots - representing valence electrons.
    
   • Dots are placed on the four sides of the chemical symbol; top, bottom, left, and right.
      
   • Each side can accommodate up to two electrons, like an orbital.
      
   • All sides of the symbol are equivalent, which means that the choice of which side to place two electrons versus one electron is arbitrary. Remember that electrons enter empty orbitals when available.
     

   • Notice that the number of dots (valence electrons) in each diagram above is the same as the group number of the element.