1 group 7 Alevel考试化学课件.pptx

GroupⅦIntroductionGeneralpropertiesoftheGroupⅦelementsThereactivityofthehalogens:displacementreactions

Introduction

AlltheelementsinGroupⅦarenon-metalsexceptforastatine,whichisaradioactivemetalloid.Theseelementsarecalledhalogens,whichmeans“salt-former.”Allofthehalogensformsaltswithsodiumandwiththeotheralkalimetals.

Thehalogenfluorineisthemostreactiveofthehalogensincombiningwithotherelements.Chlorineislessreactivethanfluorine,andbromineislessreactivethanchlorine.Iodineistheleastreactiveofthefournonmetals.

Somefacts…1)ReactivityDECREASESasyougodownthegroupDecreasingreactivity(Thisisbecausetheelectronsarefurtherawayfromthenucleusandsoanyextraelectronsaren’tattractedasmuch).2)Theyexistasdiatomicmolecules(sothattheybothhaveafulloutershell):ClCl3)Becauseofthisfluorineandchlorinearegasatroomtemperatureandbromineisaliquid

GeneralpropertiesoftheGroupⅦelements

Theybehavechemicallyinasimilarway;Theyarenon-metals;Theyallexistasdiatomicmoleculesatroomtemperature;Theirmeltingandboilingpointsincreasewithincreasingatomicnumber;Thecolouroftheelementsdeepenswithincreasingatomicnumber;Theyareveryreactiveandreadilyformsalts;

Incompoundsahalogenatomincreasesitsshareofelectronsfromseventoeightbyionicorcovalentbonding;ThereactivityoftheelementsdecreasesondescendingtheGroup;Theyexhibitarangeofoxidationstates;TheelectronegativityoftheelementsdecreasesondescendingtheGroup;TheiroxidisingabilitydecreasesondescendingtheGroup;

Thereactivityofthehalogens:

displacementreactions

Thefirstelectronaffinityreferstotheenthalpychangeforthefollowingprocess:

Electronaffinity

DisplacementreactionAreactioninwhichoneelementproducesanotherfromanaqueoussolutionofitsions.

Chlorinedisplacesbromineandiodine:

brominedisplacesi