Final answer:
Fluorine (F) has the greatest first ionization energy among the listed elements (Rb, F, Li, Fr) because it is positioned at the top right in its group on the periodic table, indicating higher ionization energy.
Step-by-step explanation:
The question is asking which element has the greatest first ionization energy: Rb, F, Li, or Fr. Ionization energy tends to increase across a period from left to right and decrease down a group on the periodic table. Among the elements listed, fluorine (F) has the highest first ionization energy because it is the furthest to the right and top of its group compared to the other elements.
Therefore, the correct answer is b) F, as fluorine is in the top right corner of the list of elements provided, signifying it has the highest ionization energy in its set.