Consider the alkali metals in the periodic table. Which element has the smallest atomic radius?

• A. Li
• B. Na
• C. K
• D. Rb

Answer: (A)

Verified step by step guidance

1. Recall that alkali metals are elements in Group 1 of the periodic table, including Li, Na, K, and Rb.
2. Understand that atomic radius generally increases as you move down a group in the periodic table because each successive element has an additional electron shell.
3. Compare the positions of Li, Na, K, and Rb in Group 1: Li is in period 2, Na in period 3, K in period 4, and Rb in period 5.
4. Since Li is at the top of the group with the fewest electron shells, it has the smallest atomic radius among these elements.
5. Therefore, the element with the smallest atomic radius among Li, Na, K, and Rb is Li.