Question

why ionisation energy is maximum for inner gases??​

Answer 1

are highly unreactive because its outermost atomic orbital has been filled to its maximum capacity of 8 electrons. Electrons in an atom's outermost atomic orbital are called, "valence electrons." ... As a result, more energy (ionization energy) is required to "pull" a valence electron away from inert gases.

Answer 2

ionization energy is used to remove valance electron from the elements but we know that inert gas is stable so, it require maximum energy.