Which of these elements in group 1a has the largest atomic radius? cesium, rubidium, potassium, or sodium?

Option (a) is the correct answer.

Explanation:

It is known that when we move down a group then there occurs an increase in the size elements due to the addition of more number of electrons into new shells.

Hence, it means that atomic radius of the elements also increases.

For the given group 1A elements, sodium is at the top so it has smaller atomic radius whereas cesium is at the bottom. Therefore, cesium has the largest atomic radius.

Thus, we can conclude that cesium elements in group 1A has the largest atomic radius.