Question

Which of the following halogens has the largest atomic radius?

Answer 1

Answer:

$\boxed {\boxed {\sf B. \ Iodine }}$

Explanation:

Atomic radius is the measurement from the nucleus to the outer edge of the electron cloud.

As you go down a group (vertically) the atomic radius increases because more electron shells are added. As you go across a period horizontally, the atomic radius decreases.  

If we look at the halogens group (17), we see they follow this order from top to bottom:

F - Fluorine

Cl - Chlorine

Br - Bromine

I - Iodine

Since it increases down the group, iodine  must have the largest atomic radius.