Concept:Atomic radius decreases from left to right across a period due to increasing effective nuclear charge.
Formula:$$ Z_{\text{eff}} \uparrow \implies \text{Atomic Radius} \downarrow $$
Solution:- All the given elements (Na, Mg, P, S) belong to Period 3 of the periodic table.
- Their order from left to right is: Na (Group 1), Mg (Group 2), P (Group 15), S (Group 16).
- Sulfur (S) is the furthest to the right. It has the highest number of protons (highest nuclear charge) pulling on the same shell of electrons, compressing the atom to the smallest size among the options.
Why other options are incorrect:- Option A, Option C, Option D: These elements sit further to the left, meaning they have lower effective nuclear charges and comparatively larger atomic radii.
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