Explain why the Ionisation potential of inert gases are very high white that of alkali metals are very low.

Explanation

Outermost shells of inert gases contain octet of electrons. Besides this, each of the inner shels of inert gas elements is fully filled such configuration is exceptionally stable obviously, conversion of a neutral inert gas atom into its ions by removal of an electron from outermost shell required a large energy. as a result, they have high ionisation potential.
Configuration of the outermost and penultimate shell of alkali metals is `(n-1)s^(2)(n-1)p^(6)ns^(1)` (except 1.1). thus loss of 1 electron from their outermost shell brings about stable configuration of inert gases. hence, conversion of alkali metals to their ions requires comparatively less amount of energy as a result, alkali metals have low vlaues of ionisation potential.