Here's why:

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

* Electron Configuration: The electron configuration of fluorine is 1s² 2s² 2p⁵.

* Valence Shell: The outermost shell containing electrons is considered the valence shell. In this case, the 2s and 2p orbitals are the valence shell.

Therefore, the second energy level (containing 2s and 2p orbitals) is the valence shell for fluorine.