Explain Kossel - Lewis approach to chemical bonding.

Explanation

Lewis considered the atom in terms of a positively charged 'Kernel'. Kernel contains inner electrons and the nucleus. Lewis assumed that the outer shell can accommodate a maximum of eight electrons which occupy the eight coners of a cube surrounding the Kernel. He assumed this type of arrangement in noble gases and hence they are stable. The atoms which do not have this type of arrangement achieve the stable octet by combining with other atoms by sharing of electrons forming a covalent bond.
Kossel proposed that the highly electronegative elements like halogens gain electrons and convert into anions. The highly electropositive alkali metals lose electrons and convert into positive ions. During their conversion into ions they get the noble gas configuration. i.e., octet and thus get stability. Now the positive and negative ions unite together by electrostatic attraction between them.
Thus Lewis proposed the covalent bond formation and Kossel proposed the ionic bond formation.