Question

has the largest atomic radius
a cs
b pb
c br
d se

Explanation:

Atomic radius trends: increases down a group and decreases across a period. Cs (cesium) is in Group 1 (alkali metals), period 6. Pb (lead) is in Group 14, period 6. Br (bromine) is in Group 17, period 4. Se (selenium) is in Group 16, period 4. Since Cs is in the left - most group (Group 1) among the elements with the highest period number (period 6) in the given options, it has the largest atomic radius.

Answer:

A. Cs