Which of the following atoms has the largest atomic radius?

• A. K
• B. Li
• C. Mg
• D. Na

Answer: (D)

Verified step by step guidance

1. Recall that atomic radius generally increases as you move down a group (column) in the periodic table because additional electron shells are added, making the atom larger.
2. Recall that atomic radius generally decreases as you move from left to right across a period (row) in the periodic table because the increasing nuclear charge pulls electrons closer to the nucleus.
3. Identify the positions of the given elements: Li (Lithium) is in period 2, group 1; Na (Sodium) is in period 3, group 1; K (Potassium) is in period 4, group 1; Mg (Magnesium) is in period 3, group 2.
4. Compare the elements by their group and period: K is below Na and Li in group 1, so it should have the largest radius; Mg is to the right of Na in period 3, so it should have a smaller radius than Na.
5. Since K is in period 4 and group 1, it has the largest atomic radius among the listed atoms, which contradicts the given answer. Therefore, re-examine the problem or answer key for possible errors.