Arrange the following elements in order of increasing atomic radius: Na, Mg, Al, Si.

• A. Si < Al < Mg < Na
• B. Al < Si < Na < Mg
• C. Mg < Na < Si < Al
• D. Na < Mg < Al < Si

Answer: (A)

Verified step by step guidance

1. Recall that atomic radius generally decreases from left to right across a period in the periodic table due to increasing nuclear charge pulling electrons closer to the nucleus.
2. Identify the position of each element (Na, Mg, Al, Si) in the periodic table. All are in the same period (Period 3), with Na on the far left and Si towards the right.
3. Understand that as you move from Na to Si across the period, the atomic radius decreases because the number of protons increases, pulling the electron cloud closer without adding extra electron shells.
4. Arrange the elements from smallest to largest atomic radius based on their position: Si (smallest), then Al, then Mg, and finally Na (largest).
5. Confirm that the order of increasing atomic radius is Si < Al < Mg < Na.