Which of the following atoms has the largest atomic radius?

• A. Mg
• B. Al
• C. Na
• D. Si

Answer: (C)

Verified step by step guidance

1. Recall that atomic radius generally decreases across a period (left to right) in the periodic table due to increasing nuclear charge pulling electrons closer to the nucleus.
2. Identify the positions of the given elements in the periodic table: Na (Sodium) is in Group 1, Period 3; Mg (Magnesium) is in Group 2, Period 3; Al (Aluminum) is in Group 13, Period 3; Si (Silicon) is in Group 14, Period 3.
3. Since all these elements are in the same period (Period 3), compare their group numbers to determine their relative atomic radii. Elements further to the left in the period have larger atomic radii.
4. Recognize that Na is furthest to the left among the given elements, so it has the least effective nuclear charge experienced by the outer electrons, resulting in the largest atomic radius.
5. Conclude that Na has the largest atomic radius among the listed atoms because atomic radius decreases from left to right across a period.