Which of the following metals would be expected to have the smallest atomic radius?

• A. K
• B. Li
• C. Rb
• D. Na

Answer: (B)

Verified step by step guidance

1. Understand that atomic radius generally decreases across a period (left to right) in the periodic table and increases down a group (top to bottom).
2. Identify the group and period of each metal: Li, Na, K, and Rb are all in Group 1 (alkali metals), but in different periods.
3. Recognize that as you move down Group 1 from Li to Rb, the atomic radius increases because each element has an additional electron shell.
4. Since Li is at the top of Group 1, it has the fewest electron shells and thus the smallest atomic radius among the given options.
5. Conclude that Li has the smallest atomic radius because it is the lightest alkali metal with the least number of electron shells.