Concept:When a non-metal gains an electron to form an anion, electron-electron repulsion increases within the valence shell. Because the nuclear charge remains the same, the electron cloud expands, making the anionic radius significantly larger than its parent neutral atom.
Solution:- The actual atomic size of a neutral Fluorine (F) atom is 72 pm.
- When it gains one electron to form the Fluoride ion (\( \text{F}^- \)), the added repulsion causes the radius to expand.
- According to standard textbook values, the ionic radius of \( \text{F}^- \) increases to 136 pm.
Why other options are incorrect:- Option A: 72 pm is the covalent radius of the neutral F atom.
- Options C & D: These values correspond to the atomic/ionic radii of larger halogens or elements, not fluorine.
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