Write the postulate of Kossel for the formation of an ionic bond.

(N/A) In the periodic table,the highly electronegative halogens and the highly electropositive alkali metals are separated by the noble gases.
The formation of a negative ion from a halogen atom and a positive ion from an alkali metal atom is associated with the gain and loss of an electron by the respective atoms.
The negative and positive ions thus formed attain stable noble gas electronic configurations. The noble gases (with the exception of helium which has a duplet of electrons) have a particularly stable outer shell configuration of eight (octet) electrons $ns^{2} np^{6}$.
The negative and positive ions are stabilized by electrostatic attraction.
Kossel's postulation provides the basis for modern concepts regarding ion-formation by electron transfer and the formation of ionic crystalline compounds.