Question

which of the following atoms is the largest?
u
k
na
cs
rb

Explanation:

Atomic radius increases down a group in the periodic table. Among the given elements (Li - Lithium, K - Potassium, Na - Sodium, Cs - Cesium, Rb - Rubidium), they are all in Group 1 (alkali metals). Cesium (Cs) is the lowest - placed among them in the group.

Answer:

Cs