§17 The halogens 17.1 The halogens 17.2 The elemental substances 17.3 Hydrogen halides 17.4 Halides and Polyhalides 17.5 halogen oxyacids §17 The halogens 17.5 halogen oxyacids 17.4 Halides and Polyhalides 17.3 Hydrogen halides 17.2 The elemental substances 17.1 The halogens