Kossel in relation to chemical bonding drew attention to the following facts –
(i) In the periodic table, the highly electronegative halogens and the highly electropositive alkali metals are separated by the noble gases.
(ii) In the formation of a negative ion from a halogen atom and a positive ion from an alkali metal, atom is associated with a gain and loss of an electron by the respective atoms.
(iii) The negative and positive ions so formed attain stable noble gas electronic configurations. The noble gases have particularly eight electrons, ns2 np6.
(iv) The –ve and +ve ions are stabilized by electrostatic attraction.
