Answer: Group 2: alkaline earth metals.
Explanation: The second ionization energy is the energy required so that the molecule in the gaseous state would lose its second valence electron. Since all atoms tend to stabilize by having complete number of electrons in the valence shell (octet rule), thus, the elements having the lowest second ionozation energy will be those having 2 electrons in the outermost shell (the first ionozation energy removes the first outermost electron while the second ionozation energy removes the second one , thus, turning the atom into the stable state)
