Answer:
Cesium
Step-by-step explanation:
The atomic radius is the distance between the nucleus and the outermost orbital of an atom. By the atomic radius, it is possible to determine the size of the atom.
The atomic radius is a periodic trend that means that it is a specific pattern in the properties of the chemical elements that are revealed in the periodic table
This property increases as follows (see attached file)
Therefore the element that is lower in the group is the one with the largest radius
In this case, the one located below in the group is cesium, that is, the one with the largest radius