Which of the following alkali metals has the largest atomic radius?

• A. Cs
• B. Na
• C. K
• D. Li

Answer: (A)

Verified step by step guidance

1. Recall that atomic radius generally increases as you move down a group in the periodic table because each successive element has an additional electron shell, making the atom larger.
2. Identify that all the given elements (Li, Na, K, Cs) are alkali metals located in Group 1 of the periodic table.
3. Determine the position of each element in the group: Li is in period 2, Na in period 3, K in period 4, and Cs in period 6.
4. Understand that since Cs is the lowest in the group among the options, it has the most electron shells and therefore the largest atomic radius.
5. Conclude that the atomic radius increases in the order Li < Na < K < Cs, so Cs has the largest atomic radius.