Here's why:

* Electronegativity: Fluorine is the most electronegative element on the periodic table. This means it has a strong attraction for electrons.

* Tendency to Gain Electrons: To achieve a stable electron configuration like that of the noble gases, fluorine needs to gain one electron.

* Formation of F^-: By gaining an electron, fluorine becomes a negatively charged ion, known as fluoride (F^-).

Let me know if you have any other questions!