Question

1. why does f not shrink when it gains electrons to form its most common ion, f?

Explanation:

Fluorine (F) has 9 protons and 9 electrons in its neutral state. When it gains an electron to form \( F^- \), the number of electrons becomes 10 while protons remain 9. The electron - electron repulsions increase as there are more electrons in the same electron cloud (valence shell for F is \( n = 2 \), and after gaining an electron, the electrons are still in the same principal energy level). The attractive force from the nucleus (due to protons) is now distributed over more electrons, so the electron cloud expands instead of shrinking. The key is the change in electron - electron repulsions and the distribution of nuclear charge over a greater number of electrons in the same energy level.

Answer:

When F gains an electron to form \( F^- \), the number of electrons (10) exceeds the number of protons (9). Electron - electron repulsions in the same valence shell (\( n = 2 \)) increase, and the nuclear charge is spread over more electrons, causing the electron cloud to expand (not shrink).