15.1.1 The halogens Properties of the halogens: Elements(VII) F CI Br I Valence electron 2s22p5 3s23p5 4s24p5 5s25p5 configuration Atomic radius/pm 64 99 114 133 Electronegativity 3.98 3.16 2.96 2.66 Ionization energy 16811251 1140 /kJmol-1 1008 Electron affinity -328回 -349 -325 -295 energy /kJ.mol-1 Oxidation number -1 1,1,3,5,7Properties of the halogens ： Elements(VII) F Cl Br I Valence electron 2s 22p5 3s 23p5 4s 24p5 5s 25p 5 configuration Atomic radius/pm 64 99 114 133 Ionization energy /kJ·mol-1 1681 1251 1140 1008 Electronegativity 3.98 2.96 3.16 2.66 Electron affinity energy /kJ·mol-1 -328 -349 -325 -295 Oxidation number - 1 -1 ， 1 ， 3 ， 5 ， 7 15.1.1 The halogens z1