Which element has the smallest atomic radius?

• A. Chlorine (Cl)
• B. Sodium (Na)
• C. Lithium (Li)
• D. Fluorine (F)

Answer: (D)

Verified step by step guidance

1. Understand that atomic radius refers to the size of an atom, typically measured from the nucleus to the outer boundary of the electron cloud.
2. Recall the periodic trends: atomic radius decreases from left to right across a period due to increasing nuclear charge pulling electrons closer, and increases down a group because additional electron shells are added.
3. Identify the positions of the given elements on the periodic table: Sodium (Na) and Lithium (Li) are in Group 1 (alkali metals), Chlorine (Cl) and Fluorine (F) are in Group 17 (halogens), with Fluorine above Chlorine.
4. Compare elements within the same period: Fluorine and Chlorine are in the same group but different periods, so Fluorine has a smaller atomic radius because it is higher up (fewer electron shells).
5. Compare elements across the period: Fluorine is to the right of Sodium and Lithium, so it has a smaller atomic radius due to higher effective nuclear charge pulling electrons closer.