Answer:
The ion with the largest size is Cs+.
Step-by-step explanation:
The size of an ion is determined by the number of electrons it contains and the arrangement of those electrons in its electron cloud. Ions with a larger number of electrons will generally have a larger size because their electron clouds will be more diffuse and occupy more space. Ions with a smaller number of electrons will have a smaller size because their electron clouds will be more compact.
In general, ions in the same group of the periodic table will have a similar number of valence electrons and will be similar in size. For example, the F- ion and the O-2 ion both belong to Group 17 and have 7 valence electrons, so they are expected to be similar in size. Similarly, the Cs+ and Al+3 ions both belong to Group 1 and have a single valence electron, so they are also expected to be similar in size.
However, the Cs+ ion is much larger than the Al+3 ion because it has a larger number of total electrons. Cs+ has 55 electrons, while Al+3 has only 13 electrons. The larger number of electrons in Cs+ results in a more diffuse electron cloud and a larger overall size. Therefore, among the ions listed, Cs+ has the largest size