Which of the following elements has the largest atomic radius?

Correct answer: (a) Lithium

Explanation

Lithium, beryllium and boron are all in period 2. Across a period the nuclear charge grows while electrons enter the same shell, so the atomic radius decreases from left to right.

Lithium, the first of the three, is the largest: about 152 pm, against about 112 pm for beryllium and 85 pm for boron.