Here's why:

* Atomic Radius: Atomic radius is the distance between the nucleus and the outermost electron shell of an atom. Fluorine has a smaller atomic radius than carbon.

* Electronegativity: Fluorine is the most electronegative element, meaning it has a strong attraction for electrons. This strong attraction pulls the electrons closer to the nucleus, making the atomic radius smaller.

* Nuclear Charge: Fluorine has a higher nuclear charge (more protons in the nucleus) than carbon. This stronger attraction pulls the electrons closer to the nucleus, further reducing the atomic radius.

In summary, the smaller atomic radius of fluorine compared to carbon is due to its higher electronegativity and stronger nuclear charge.