Question

Do noble gases have high or low ionization energies?

Answer 1

Ionization energies increase across a Period from left to right as we face the Table............

Explanation:

.........And ionization energies decrease down a Group.

Thus Noble Gases have exceptionally high ionization energies.

Simply considerations of electrostatics should rationalize this trend. As nuclear charge increases in the same Period, ionization energy progressively increases. It reaches a maximum when the valence electronic shell is complete.

This diagram is well-used, and illustrative.