Here's why:

* Atomic Number: Fluorine has an atomic number of 9, meaning it has 9 protons and 9 electrons. Hydrogen has an atomic number of 1, meaning it has 1 proton and 1 electron.

* Electron Shells: Fluorine has 2 electron shells, while hydrogen only has 1. The more electron shells an atom has, the larger its atomic radius.

* Electronegativity: Fluorine is the most electronegative element, meaning it attracts electrons more strongly. This makes its electron cloud denser and more compact.

In summary: Although fluorine has a smaller nuclear charge than chlorine, its greater electronegativity and additional electron shell make it a larger atom.