Which of the following elements has the largest atomic radius?

• A. Al
• B. Na
• C. Mg
• D. Si

Answer: (B)

Verified step by step guidance

1. Recall that atomic radius generally increases as you move down a group in the periodic table and decreases as you move from left to right across a period.
2. Identify the positions of the elements Al, Na, Mg, and Si on the periodic table. All these elements are in the same period (Period 3), but they belong to different groups.
3. Since all elements are in Period 3, the trend to consider is the decrease in atomic radius from left to right across the period due to increasing nuclear charge pulling electrons closer.
4. Compare the group numbers: Na is in Group 1, Mg in Group 2, Al in Group 13, and Si in Group 14. The element furthest to the left (Na) will have the largest atomic radius.
5. Conclude that Na has the largest atomic radius among the given elements because it has the least nuclear charge pulling on its electrons in the same period.