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Chemistry C3 Topic 1 Revision PowerPoint 1 The Periodic Table This PowerPoint covers Topic 1 Lessons 1 to 6 C3_1Keywords What I’m Looking For 1) Explain the contribution Newlands and Mendeleev made to the development of the Periodic Table 2) Identify the problems which arose from using atomic weights rather than atomic numbers in organising elements WILF1 Atomicweights Newlands Lawofoctaves Duringthe1860sNewlandsgroupedthe56elementshe knewaboutinorderoftheiratomicweights.Henoticed thateveryeighthelementhadsimilarproperties. Theatomicweightofanelementisthetermwhich19th andearly20th centuryscientistsusedthen– nowadaysweuse(relative)atomicmass. Inthe1860’s,Newlandswasinterestedinthepatternsinbehaviourof the56elementsheknewof,witheveryeighthelementshadsimilar properties.Heusedthispatternandputforwardhislawofoctaves after themusicscale. Groupsofelements GroupsareverticalcolumnsinthePeriodicTablecontainelementswith verysimilarchemicalproperties. Periods ElementsinthesameperiodofthePeriodicTablehaveatomswhichare buildingupthesameelectronshell.Period4elementshavefourshells ofelectrons,withthefourthshellbeingfilled.Periodsstartwithvery reactivemetal,thenlessreactivemetalsfollowedbynon-metalsand thenreactivenon-metals.Finallytheperiodendswithanoblegas. Hecalledhisdiscoverythelawofoctaves. Heforcedsomeelements intounnaturalgroupings, e.g.heplacedcopperinthe samegroupaslithium, sodiumandpotassium,and nickelinamongstfluorine, chlorineandbromine. WILF1 WILF1 Mendeleev Mendeleevcontinued In1869Mendeleevusedinformationaboutelements, includingitschemicalpropertiesandatomicweight.He recordtheinformationoncardsandplacedtheelements inincreasingorderoftheiratomicweightsbutgrouped similarelementstogether. ThiswasthefirstPeriodicTable. Mendeleevrealisedhistablewasnotperfectanddidn’t forceelementsintounnaturalgroups,likeNewlandshad done,insteadleftgapswherehefeltsomeyet undiscoveredelementsshouldbe.Healsorealisedthat somepairsofelementsliketelluriumandiodineseemed tobeinthewronggroup.Heswappedthemover;iodine isverysimilartobromineandchlorine. WILF2 Inthe‘modern’periodictable,elementswereorganisedin increasingatomicnumber(protonnumber) Inthe19th century,chemistsdidnotknowaboutsub-atomic particlesandorganisedtheelementsinincreasingorderof theiratomicweights.Thiscreatedsomeanomalies.The elementsiodine,atomicweight127,shouldbeinGroup6and tellurium,atomicweight128,shouldbeinGroup7. IodineisverysimilartobromineandtheotherHalogen elementsinGroup7,telluriumislikeseleniuminGroup6. Mendeleevplacedtheelementsinthecorrectgroupaccording totheirchemicalbehaviournot accordingtotheiratomic weights. Mendeleevleftgapsformissingelementsand he predictedwhattheymightbelike.Overthenextfew yearsnewelementswerediscovered: o theelementunderaluminiumwasdiscoveredbyde Boisbaudram,whocalledinGallium,andithad similarpropertiestoaluminium– justasMendeleev predicted o themissingelementscandiumwasdiscoveredby Nilson in1879and,onceagain,itsbehaviourwas thesameasMendeleevpredicted. What I’m Looking For 1) Explain the link between an element’s electronic configuration and its position in the periodic table (its period and group) 2) Make predictions about the electronic configurations of the first 20 elements from their atomic numbers and position in the table. WILF1 C3_2Keywords Atomicnumber Theatomicnumberofanelementissameasthenumberofprotonsin anatomoftheelement.Theatomicnumberalsotellsyouhowmany electronsthereareinoneatomoftheelement. Outershellelectrons Thenumberofoutershellelectronsthatanelementhasisthesameas itsgroupnumberandithasagreatinfluenceuponthechemical behaviourofthatelement. Groupsofelements GroupsareverticalcolumnsinthePeriodicTablecontainelementswith verysimilarchemicalproperties. Periods ElementsinthesameperiodofthePeriodicTablehaveatomswhichare buildingupthesameelectronshell.Period4elementshavefourshells ofelectrons,withthefourthshellbeingfilled.Periodsstartwithvery reactivemetal,thenlessreactivemetalsfollowedbynon-metalsand thenreactivenon-metals.Finallytheperiodendswithanoblegas. WILF2 Numberofelements Ifelementsarearrangedinincreasingorderofatomicnumber, theproblemswithelementsliketelluriumandiodinearesolved. Elementsinthesamegrouphavethesamenumberofoutershell electrons.Itisthenumberofoutershellelectronswhich determineshowtheelementbehaves.Chlorineandbromine behaveverysimilarlytooneanotherbecausechlorineatomsand bromineatomshavesevenoutershellelectrons.Theirchemical reactionsaredominatedbytheirdesiretogainoneextraelectron andcompletelyfilltheoutershellofelectrons. Thelinkbetweenelectronstructureandbehaviourallowsusto makepredictionsaboutthebehaviourandreactivityofelements inthesamegroup. Element Atomic Number Electronic structure GroupNumber PeriodNumber Helium 2 2, ‘0’ 1 Lithium 3 2,1 1 2 Oxygen 8 2,6 6 2 Neon 10 2,8 ‘0’ 2 Numberofelectronsallowedin the‘shell’ Sodium 11 2,8,1 1 3 Sulphur 16 2,8,6 6 3 Potassium 19 2,8,8,1 1 4 Elementsarearrangedinperiods.Thenumberof elementsineachperiodtellsyouthenumberof electronsthatcanbeaddedtothatshell. Period Number Theatomicnumberoftheelementisthenumberofprotons presentinoneatomoftheelement.Thisisalsoequaltothe numberofelectronsintheatom. 1 2 2 2 8 8 3 8(thenanextra10) 8(thenupto18) 4 8(thenanextra 10,thenan extra14) 8,thenupto18andthenup32 Weneedtobeabletoworkouttheelectronstructuresof thefirsttwentyelements,afterwhichthingsget complicated! Elementsmadeofatomswiththesamenumberofoutershellelectrons behaveinavery similarway.Theywillbeinthesamegroup oftheperiodic table. Usingtheelementsinthesmalltableabove: o heliumandneonbehavesimilarly(theydonotdoreactwithanything) o oxygenandsulphurbehavesimilarly(formcompoundswithhydrogen – similarformulae– H2OandH2S) o lithium.sodiumandpotassiumbehavesimilarly(formchlorideswith theformulaXCl;reactveryvigorouslywithwatertoformhydrogen) What I’m Looking For C3_3Keywords Fulloutershellofelectrons 1) List three physical and three chemical properties of the alkali metals lithium, sodium and potassium. 2) Explain why potassium atoms prefer to form positive ions rather than remain as an element. Elementswithatomsthathaveacompletelyfulloutershellof electrons areverystableandunreactive.Group1elementshave atomswithoneoutershellelectron,whichmakesthemunstable chemically– sotheseatomsreadilylosethisoutershellelectron andformastablepositiveion.Theionhasafulloutershellof electrons. Na = 2,8,1 Na+ +e2,8 Theionispositivelycharged(GENPILE)becausetheionhas11 protons(+)andonly10electrons(-). 2,8,1and2,8representstheelectronconfiguration(electron arrangement)ofasodiumatomandasodiumionrespectively. WILF1 Group1TheAlkaliMetalelements Group1TheAlkaliMetalelements Chemicalproperties TheAlkalimetalelementsareaGroupofveryhighlyreactive metalswithsimilarchemicalandphysicalproperties o TheAlkalimetalsliketoreactwithnonmetalelementssuchasoxygenand chlorine,formingmetaloxidesandmetal chloridecompoundsthatcontainions, e.g.Na2O[2Na+;O2-],NaCl [Na+;Cl-] Physicalproperties o TheAlkalimetalsaresoftenoughtobecutwithaknife o TheAlkalimetalshavelowdensitiesformetals:lithium, sodiumandpotassiumfloatonwater,howeverrubidiumand caesiumaremoredensethanwater o Alkalimetalshavemuchlowermeltingandboilingpointsthan othertraditionalmetals;sodiummeltswhenitreactswith waterasdoespotassium o Thereactionswithchlorinearevery vigorous,exothermicreactions 2K(s) +Cl2 (g) =2KCl (s) WILF2 Fulloutershellofelectrons Elementswithatomsthathaveacompletelyfulloutershellof electrons areverystableandunreactive.Group1elementshave atomswithoneoutershellelectron,whichmakesthemunstable chemically– sotheseatomsreadilylosethisoutershellelectron andformastablepositiveion.Theionhasafulloutershellof electrons. K 2,8,8,1 = K+ +e- 2,8,8 Theionispositivelycharged(GENPILE)becausetheionhas19 protons(+)andonly18electrons(-). 2,8,8,1and2,8,8representstheelectronconfiguration(electron arrangement)ofapotassiumatomanditsionrespectively. WILF1 Group1Metalsreactvigorouslywithoxygen Group1metalsareaproblemtostorebecausethemetalquickly oxidisesifleftexposedtoair.Eachmetalisstoredunderparaffin oil,preventingairandwater,substancescontainingoxygen,from attackingthem. Whenfreshlycutmetalisexposedtoair,lithiumtakes12seconds totarnish,sodiumabout3secondsandpotassiumlessthana second.Theyformoxideswhichmakestheshinymetalchangeto agreyishoxide. sodium+oxygen=sodiumoxide 4Na(s) +O2(g) =2Na2O(s) Sodiumoxideisawhitesolidthatdissolvesreadilywatertomake analkalinesolutionofsodiumhydroxide. What I’m Looking For 1) Describe the reactions of the alkali metals with oxygen and with water in detail with balanced equations 2) Explain why potassium is more reactive than sodium using the ideas of nuclear attraction force and electron shielding. (High Demand) Group1Metalsreactvigorouslywithwater Whenfreshlycutmetalisaddedtoatroughofwaterthereisa rapidreactionthatproducesbubblesofhydrogengasandleavesa colourlesssolutionofastronglyalkalinemetalhydroxide. lithium+water=sodiumhydroxide+hydrogen 2Li(s) +2H2O(l) =2LiOH(aq) +H2(g) Lithiumreactsquicklywithwater,sodiumreactsmuchfasterand morevigorouslywithwater,andthereactionismoreexothermic sothesodiummetalmelts. Potassiummetalreactssoquicklyandsoviolentlythatthe potassiummetalmeltsduringthereactionandgetshotenough forthehydrogenbubblestocatchfire. Thisreactionshowsthatreactivityincreasesdownthegroup. Lithium<Sodium<Potassiumandthispatterncontinuesdown thegroup. WILF2 ThereactivityoftheGroup1metalsincreasesasyou descendthegroupfromlithiumtocaesium.Intheir chemicalreactionsthemetalatomswanttolosetheir outershellelectronandformastableionwithfull outershellofelectrons. Asyoudescendthegroupfromlithiumtopotassium theoutershellelectrontobelost: o isfurtherfromthenucleus o isshieldedbymoreandmorefullinnershellsof electron(thisiscalledelectronshellshielding) What I’m Looking For So,theoutershellelectroninalarge potassiumatomexperiencesamuch weakernuclearattractionforcefrom thepositivelychargedatomicnucleus. Apotassiumatomgivesawayitsouter shellelectronmuchmorereadilythan asodiumoralithiumatom,whichis whypotassiumreactssomuchmore violentlywithoxygen,chlorineand water. Potassiumis‘moreelectropositive’ thansodiumbecauseitlikestoform positiveionsmorereadilythan sodiumorlithium WILF1 TheTransitionmetals ThesemetalslieinthemiddleofthePeriodictablebetween Groups2and3. 1) Compare the physical behaviour of transition metals with those of the alkali metals 2) Compare the chemical properties of transition metals with those of the alkali metals LiketheGroup1Alkalimetals,Transitionelementsare: o goodconductorsofheatandelectricity o areshinywhenfreshlycut UnliketheGroup1Alkalimetals,Transitionelements: o havemuchhigherdensities o aremuchharderandstronger o havemuchhighermeltingandboilingpoints(except mercuryofcourse!) Transitionelementshaveverycolourful compounds(oxidesandsalts)andthe metalsandtheircompoundsmakeexcellent catalysts. Transitionelementshavetheabilitytoform ionsofdifferentcharges;thisiscalled variablevalency. e.g.ironformstwotypesofion,Fe3+ and Fe2+ andthesecompoundshavedifferent appearances. o areductile(canbedrawnintowires)andmalleable(canbe shapedintosheetsandpipes) Transitionelementshaveverycolourfulcompounds.Transition metalsandtheircompoundsmakeexcellentcatalysts. iron(II)sulphateisgreenandiron(III)sulphateisreddish-brown WILF2 What I’m Looking For Transitionelementsarenowherenearasreactive towardsairandwaterastheAlkalimetals. Alkalimetalsreactimmediatelyoncontactwithwater whereassomeTransitionelementseitherreactvery slowlywithwater,ordonotreactatall. Ironreactsveryslowlywithcoldwaterbutfaster whenheatedinsteam.Rust,hydratedironoxide,is formed. Goldandplatinumdonotreactwithwater,which makesthemsuitableasjewellerymetalsandgoldis usedinelectricalconnectionsforcomputers. 1) Compare the similarities and differences in the reactions of the halogen elements with iron 2) Make predictions about the outcomes of halogen / halide salt solution reactions 3) Explain why fluorine is a more reactive than chlorine HalogenElements TheseelementsarefoundinGroup7ofthePeriodicTable. Halogensreactwithmetalssuchasironwoolandsodium. Halogenelementsexistasdiatomicmolecules,e.g.Cl2 Halogensarecolourfulelementswiththecoloursbecoming darkerandmoreintenseasyoudescendthegroup.Meltingand boilingpointsincreaseareyoudescendthegroup. WILF1 Group7Halogenelementsandiron Fluorine reactsvigorouslywithironwoolinthecoldand immediatelyoncontactwiththemetal.Iron(III)fluorideis producedinthereaction. 2Fe(s) +3F2(g) =2FeF3(s) Agasjarofchlorinereactswithhotironwoolandproduces brownfumesofiron(III)chloride.Thereactionisrapidand givesoutheat(exothermic). Ironreactswithbrominevapourwhenheatedinatubetoavery hightemperature.Iron(III)bromideistheproduct,butthe reactionisslow. Redhotironreactswithiodinevapourtomakeiron(III)iodide. Iron(III)iodideisunstableanddecomposestogiveirona bromineinareversiblereaction. WILF2 Group7Halogenelementsanddisplacementreactions ThereactivityoftheHalogenelements decreasesasyoudescendGroup7. Fluorineistoodangeroustotry. Inreactionsbetweentheother halogensandsolutionsoftheir potassiumsaltswecanpredictthatthe morereactivehalogen,chlorine,will displacebrominefrompotassium bromidesolution,andiodinefrom potassiumiodidesolution.The experimentsshowthereactivity pattern:chlorine>bromine>iodine Whenchlorineisbubblesthroughpotassiumbromidesolution, thepaleyellowsolutionbecomesorangeduetotheformation ofbromine.Chlorinereactstoformpotassiumchloride solution. 2FeBr3 (aq) +3Cl2(g) =2FeCl3 (aq) +3Br2(g) Thisreactionhappensbecausechlorineismorereactivethan bromine.Thereversereaction,potassiumchloridesolution andbromineisimpossible,becausebromineislessreactive thanchlorine. Halogen/halideiondisplacementreactions o chlorinewilldisplacebrominefrompotassiumbromide solutionandiodinefrompotassiumiodidesolution o brominewilldisplaceiodinefrompotassiumiodidesolution o iodinecannotdisplaceanyotherhalogen WILF3 WILF3 ThereactivityoftheHalogenelementsdecreases asyoudescendGroup7.Fluorineisthemost reactiveandiodinetheleastreactiveHalogen. FluorineisthemostreactiveHalogenbecause: Halogenatomsbecomestableionswhenthey gainanelectron,thereforetheclosertheelectron istotheatomicnucleusthemoreeasilyitis capturedbytheatom. o ithasonlyonefullinnershellofelectronssoits nucleusispoorlyshielded,chlorineatomsare biggerandhavetwofullinnerelectronshells o itsnucleusisveryclosetotheelectrontobe captured;chlorine’snucleusismuchfurtheraway Thenuclearattractionforceactingontheelectron beingcapturedismuchstrongerinthecaseof fluorineatoms,andthemuchlargeriodineatomwith fourfullinnerelectronshellsissomuchlargerthat thenuclearattractionforcebecomesmuchweaker.