Final answer:
The Group 2A element with the lowest ionization energy is barium (Ba), as it is located at the bottom of Group 2A in the periodic table, where the ionization energy is the lowest among its group due to trends in the periodic table.
Step-by-step explanation:
The Group 2A (2) element with the lowest ionization energy can be determined using the periodic trends of ionization energy across the periodic table. Since ionization energies typically increase from left to right across a period and from bottom to top within a group, the element in the bottom-left position within Group 2A will exhibit the lowest ionization energy.
Thus, for Group 2A elements specifically, the element at the bottom of the group will have the lowest ionization energy; however, the actual element Rb (rubidium) mentioned in the provided solution is not a Group 2A element, but rather belongs to Group 1. The correct answer is Ba (barium), which is the Group 2A element with the lowest ionization energy as it is at the bottom of Group 2A in the periodic table.
Electronegativity and electron shielding are important factors in understanding ionization energies. For instance, as we go down a group, electron shielding increases due to the addition of electron shells, which results in a decrease in ionization energy.
Comparatively, Group 13 elements have lower ionization energies than Group 2 elements because they have electrons in p orbitals, which are higher in energy and farther from the nucleus than the filled s orbitals in Group 2, making these electrons easier to remove. Additionally, Group 2 elements require the removal of two electrons to react, which demands more energy.