Chemistry

Question Analysis
This question assesses the student's ability to compare the atomic radii of two elements in the same group and explain the reason for the difference based on the addition of electron shells.

Key Concept Explanation
As you move down a group, the atomic radius increases due to the addition of new electron shells, which increases the distance between the nucleus and the outermost electrons. The added electron shells also provide more shielding, reducing the effective nuclear charge experienced by the outermost electrons.

Step-by-step Solution
1. Identify the elements: Potassium (K) and Rubidium (Rb) are in Group 1 (alkali metals).
2. Compare the atomic radii: Rb has a larger atomic radius than K.
3. Explain the reason: Rb has an additional electron shell compared to K, increasing the distance between the nucleus and the outermost electrons. The added electron shell provides more shielding, reducing the effective nuclear charge experienced by the outermost electrons, thus increasing the atomic radius.
4. Ther...