Fluorine will form an anion. This is because fluorine is a highly electronegative element, which means it has a strong tendency to gain electrons. In chemical reactions, fluorine typically gains one electron to achieve a stable electron configuration, similar to that of the noble gas neon.
When fluorine gains an electron, it becomes a negatively charged ion, known as an anion. The resulting ion is called fluoride, with a charge of -1. This process can be represented by the following equation:
F + e⁻ → F⁻
Fluorine does not form cations because it would require losing electrons, which is energetically unfavorable due to its high electronegativity and the stability it gains by achieving a full outer electron shell.