Question

Which one of the following elements has the largest atomic radius?

• A. Sodium
• B. Caesium
• C. Fluorine
• D. Iodine
• E. Potassium

Hint:

The element Cs (Caesium) is at the bottom of the Group 1 elements listed.
Since atomic size increases down a group, Cs must be the largest.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Atomic radius is the distance from the center of the nucleus to the outermost shell of electrons.
It follows specific periodic trends:
1. Increases down a group (due to addition of new shells).
2. Decreases across a period (due to increase in effective nuclear charge).

Step 3: Detailed Explanation:
Let's analyze the groups of the given elements:
Group 1 (Alkali Metals): Sodium (Na), Potassium (K), Caesium (Cs).
Group 17 (Halogens): Fluorine (F), Iodine (I).
In Group 1, as we go down (Na \(\to\) K \(\to\) Cs), the radius increases significantly.
In Group 17, the radius also increases down the group (F \(\to\) I), but halogen radii are always smaller than alkali metal radii in the same period because of higher nuclear charge.
Among all elements in the periodic table, atoms at the bottom-left (like Francium and Caesium) are the largest.

Step 4: Final Answer:
Caesium (Cs) has the largest atomic radius among the options.