GCSE›Edexcel GCSE Chemistry›Mind mapsGroup 7Edexcel GCSE Chemistry: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsThe halogensChlorine: pale green/yellow gasBromine: red-brown liquidIodine: grey/purple-black solidBoiling point increases down the groupReactionsMetal + halogen → metal halide2 Na+ClX2→2 NaCl\ce{2Na + Cl2 -> 2NaCl}2Na+ClX22NaClHalogen + hydrogen → hydrogen halideHydrogen halides dissolve → acidic solutionsChlorine bleaches damp litmus whiteDisplacementMore reactive halogen displaces a less reactive oneClX2+2 KBr→2 KCl+BrX2\ce{Cl2 + 2KBr -> 2KCl + Br2}ClX2+2KBr2KCl+BrX2Less reactive halogen: no reactionOrder: Cl > Br > IGroup 7the halogensClBrIAtRedoxHalogen gains electrons: reducedHalide ion loses electrons: oxidisedClX2+2 BrX−→2 ClX−+BrX2\ce{Cl2 + 2Br- -> 2Cl- + Br2}ClX2+2BrX−2ClX−+BrX2Reactivity trendReactivity decreases down the groupAtoms gain one electronMore shielding → harder to attract an electronAstatine displaced by Cl, Br and IExam tipsGroup 7 trend is opposite to Group 1Chlorine test: white, not just 'changes colour'