Here's why:

* Electron Configuration: Fluorine's electron configuration is 1s² 2s² 2p⁵.

* Valence Electrons: Valence electrons are the electrons in the outermost energy level of an atom. In fluorine's case, this is the second energy level (2s² 2p⁵).

* Total Valence Electrons: The 2s subshell has 2 electrons, and the 2p subshell has 5 electrons, giving a total of 7 valence electrons.