Lewis Theory

What is Chemical Bonding?

Chemical Bonding refers to the formation of a chemical bond between two or more atoms, molecules, or ions to give rise to a chemical compound. These chemical bonds are what keep the atoms together in the resulting compound.

Lewis Theory of Chemical Bonding

  • An atom can be viewed as a positively charged ‘Kernel’ (the nucleus plus the inner electrons) and the outer shell.
  • The outer shell can accommodate a maximum of eight electrons only.
  • The eight electrons present in the outer shell occupy the corners of a cube which surround the ‘Kernel’.
  • The atoms having octet configuration, i.e. 8 electrons in the outermost shell, thus symbolize a stable configuration.
  • Atoms can achieve this stable configuration by forming chemical bonds with other atoms. This chemical bond can be formed either by gaining or losing an electron(s) (NaCl, MgCl2) or in some cases due to the sharing of an electron (F2).
  • Only the electrons present in the outer shell, also known as the valence electrons take part in the formation of chemical bonds. Gilbert Lewis used specific notations better known as Lewis symbols to represent these valence electrons.
  • Generally, the valency of an element is either equal to the number of dots in the corresponding Lewis symbol or 8 minus the number of dots (or valence electrons)


Here, the number of dots that surround the respective symbol represents the number of valence electrons in that atom.