Which of these 2a elements has the largest atomic radius?

a. beryllium

b. magnesium

c. calcium

d. barium

e. radium

Option (E) is the correct answer.

Explanation:

When we move from top to bottom in a group then there occurs an increase in atomic size of the atoms due to increase in the number of electrons.

For example, in group 2A elements beryllium is the smallest in size whereas radium being at the bottom is the largest in size.

Also, atomic number of beryllium is 4 and atomic number of radium is 88.

Thus, we can conclude that out of the given options radium is the 2A element which has the largest atomic radius.