Question

Which of the following elements has the smallest atomic radius?

• A. Na
• B. Mg
• C. Al
• D. Si

Hint:

Across a period in the periodic table, atomic radius decreases due to increasing nuclear charge.

Answer 1

The Correct Option is D

The elements Na, Mg, Al, and Si all belong to Period 3 of the periodic table. As we move left to right across a period: - Atomic number increases - Effective nuclear charge increases - Electrons are added to the same shell, so the attraction between the nucleus and outer electrons increases. Hence, atomic radius decreases across a period. Order of atomic radius: \[ \text{Na} > \text{Mg} > \text{Al} > \text{Si} \] Answer: Therefore, Si has the smallest atomic radius among the options. Correct answer is option (4).