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 2, 7. This means:

* The first shell (n=1) has 2 electrons.

* The second shell (n=2) has 7 electrons.

* Outermost Shell: The second shell is the outermost shell for fluorine, and it contains 7 electrons.