Predict where the largest jump...

Question

Hi, the question i need help on says this:

Predict where the largest jump between successive ionization energies occur for Rb

Answer 1

Rb is in group 1, so it likes to form a 1+ cation, meaning removal of the first electron is easy and desirable. However, once the first electron is removed, Rb takes on the electron configuration of Kr (a noble gas), and is very stable. So the largest jump would be from IE1 to IE2.