The elements which occupy the peaks of the ionisation energy curve are

The second ionization enthalpy of an element is always higher than its first ionization enthalpy because

Which of the following statements is incorrect?

Which of the following elements has the highest second ionisation potential?

Suppose a gaseous mixture of $He$, $Ne$, $Ar$ and $Kr$ is treated with photons of the frequency appropriate to ionize $Ar$. What ion$(s)$ will be present in the mixture?

The first ionisation potential is maximum for