Where is the Main group atom would be expected to have the lowest second ionization energy?

The main group atom expected to have the lowest second ionization energy is typically found in Group 1 (alkali metals), particularly lithium (Li) or sodium (Na). This is because, after the removal of the first electron, these elements achieve a stable noble gas electron configuration, making it significantly easier to remove the second electron compared to other main group elements. The low effective nuclear charge felt by the remaining electrons in these atoms also contributes to their lower second ionization energy.