Fluorine has the atomic number which contain protons and electrons. ... As the number of electrons is increased, the nuclear force of attraction is decreased. Thus, the radius of fluoride ions is larger than that of fluorine atoms.
The ionic radius of fluoride is much larger than its covalent radius. When F becomes F−, it gains one electron but has the same number of protons, meaning the attraction of the protons to the electrons is weaker, and the radius is larger.
