The halogen with the smallest atomic radius is fluorine. Fluorine has an atomic radius of 1.47 Ã…, which is smaller than the atomic radii of chlorine (1.81 Ã…), bromine (2.02 Ã…), and iodine (2.66 Ã…). The small size of fluorine atoms is due to their high electronegativity, which causes them to have a strong attraction to electrons. This strong attraction results in a smaller atomic radius for fluorine compared to other halogens.