Rank the following elements in order of decreasing atomic radius: Na, Mg, Al, Si.

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

Answer: (D)

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 period 3, with Na in group 1, Mg in group 2, Al in group 13, and Si in group 14.
3. Understand that since all elements are in the same period, the atomic radius decreases as you move from left (Na) to right (Si) because the number of protons increases, increasing the effective nuclear charge and pulling electrons closer.
4. Therefore, the order of decreasing atomic radius should start with the element furthest to the left (Na) and end with the element furthest to the right (Si).
5. Conclude that the correct ranking of atomic radius from largest to smallest is: Na > Mg > Al > Si.