Final answer:
Caesium loses an electron more readily than lithium because it possesses a larger atomic radius, leading to lower ionization energy and a weaker attraction between the valence electron and the nucleus.
Step-by-step explanation:
The question is addressing why an atom of caesium loses an electron more readily than an atom of lithium. The correct answer to this question is that caesium possesses a larger atomic radius (Option C). This is because elements in the same group of the periodic table increase in size as you move down the group. Caesium is lower in the group than lithium and consequently has more electron shells, increasing its atomic radius. The larger atomic radius in caesium results in a weaker attraction between the nucleus and the valence electron, thereby lowering the ionization energy required to lose an electron. This explains why caesium readily loses an electron compared to lithium.