RevisionPackCHEMISTRY

CC1StatesofMatter

CC2SeparatingMixturesCC3AtomicStructure

CC4ElementsandPeriodicTableCC5IonicBonding

CC6Covalentbonding

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CC1StatesofMatterThethreestatesofmatteraresolid,liquidandgas,describedbelow.Stateofmatter Particlearrangement ParticlemovementSolid Neatlyarrangedinrows

TightlypackedParticlesvibrate

Liquid CloselypackedandtouchingNotorganisedintorows

Particlescanmovepasteachother

Gas Particlesseparateandonlytouchingwhentheycollide Particlesfreetomove

Gasparticleshavethemostenergywhilstsolidparticleshavetheleast.Ifsolidparticlesaregivenenoughenergy,theywillbegintomovemorevigorouslyandstarttoseparateintoasolid.Thesamewillhappenwithaliquidturningintoagas.Whensubstanceschangefromonestatetoanother,thisiscalledaphysicalchange,notachemicalchange.CC2SeparatingMixturesApuresubstanceonlyhasonetypeofsubstancepresent.Apuresubstancewillhaveanexactmelting/boilingpoint,whereasmixturescontainmorethanonetypeofsubstance,andmeltoverarangeoftemperatures.Mixturescanbeseparatedusingarangeofmethods,dependantonthemixture

Mixture SeparationTechnique ExampleSolidandliquid Filtration SandandwaterDissolvedsolidandliquid Crystallisation SaltandwaterLiquidsofdifferentboilingpoints Distillation AlcoholandwaterDifferentcoloursinink Paperchromatography RedandgreeninksImmiscibleliquids Separatingfunnel OilandwaterPurewatercanbeobtainedbya)sedimentationtoletsolidlieatthebottom,b)filtrationtoremovethesolidandc)chlorinationtokillbacteriapresent.

CC3AtomicStructureAtomsaremadeupofthreesubatomicparticles

Subatomicparticle Mass Charge Location

Proton 1 +1 NucleusElectron 1/1840(negliable) -1 OutershellsNeutron 1 0 NucleusNearlyallthemassofanatomisfoundinthenucleus,asthisiswheretheprotonsandneutronsare.Whilstanatomhasaneutralcharge(isnotanion),itwillhavethesamenumberofprotonsandelectrons,astheyareoppositelycharged.Ontheperiodictable,theatomicmassofeachelementisthelargernumber.Thistellsyouthetotalnumberofprotonsandneutrons.Theatomicnumbertellsyouthenumberofprotons.Thenumberofprotonsmatchesthenumberofelectrons.Theneutronscanbecalculatedbysubtractingtheatomicnumberfromtheatomicmass.Isotopesareversionsofatomsthathavethesamenumberofprotons,butadifferentnumberofneutrons.Forexample,thesearethethreeisotopesofHydrogen:Therelativeatomicmassofeachelementtakesintoaccounttheprevalenceofeachisotope,andcreatesaweightedaverageforeachelement.ForexampletherelativeatomicmassofChlorineiscalculatedlikethis:35Cl(75.78%)and37Cl(24.22%).(0.7578×35)+(0.2422×37)=35.48

CC4ElementsandPeriodicTableOriginally,Mendeleevarrangedtheknownelementsintogroupsbasedonthepropertiesofelementsandtheircompounds.Bylookingatpatternsinproperties,Mendeleevpredictedthepresenceofelementsthathadn’tyetbeendiscovered.Mendeleevthoughthehadarrangedelementsinorderofincreasingrelativeatomicmass,howeverthiswasnotalwaystrue,becauseoftherelativeabundanceofisotopesofsomepairsofelementsintheperiodictable.Elementsarenowarrangedinorderofatomicnumber(howmanyprotonsareinthenucleusofeachatom)Eachrowiscalledaperiod EachcolumniscalledagroupThegroupofmetalsinthemiddlearecalledthetransitionmetals.Elementsingroupshavesimilarproperties.EachperiodmatchestoanewshellofelectronsaroundthenucleusThelinebetweenAlandSi,anddowntoLvandUusseparatesthemetals(ontheleft)andnon-metals(ontheright).Isanatomisneutral(notachargedion),thenumberofelectronsequalsthenumberofprotons.Electronsarearrangedinshellsaroundthenucleus.2electronscanfitontothefirstshell8electronscanfitontothesecondandthirdshellOnceoneshellisfull,theelectronsarethendrawnonthenextshell.Electronsaredrawnassmalldotsorcrossesoncircularshells.Thenumberofelectronsineachshelliscalledtheelectronicconfiguration.Thisiswrittenwithnumbersandcommas,forexample,theelectronicconfigurationofOxygenis2,6forcalciumitis2,8,8,2.

CC5IonicBondingElectronscantransferfromoneatomtoanother.Theymaydothissothattheatomshaveafulloutershellofelectronsandarethereforestable.Ifanatomgainselectron(s)itbecomesmorenegative.Ifitloseselectron(s)itbecomesmorepositive.Ifanatomgains2electrons,ithasachargeof2-Ifitloses3electrons,ithasachargeof3+(etc).Onceanatomhasapositiveornegativecharge,itiscalledanion.Atomsingroup1have1electronintheiroutershell,andthereforeeasilyform1+ionsbylosingthiselectron.Thisgivesthemafulloutershell. Atomsingroup7however,have7electronsintheiroutershell,andeasilyform1-ionsbygaininganelectrontoforma fulloutershell.Atomsingroup6readilyform2-ionsbygainingtwoelectrons.Atomscangettheseelectronsfromotheratomsthataregaining/losingelectrons.Metals(whicheasilyloseelectrons)andnon-metals(gainingelectrons)thereforebondtogetherbydonatingelectrons. Apositivemetalionthenattractstoanegativenon-metalion,toformanionicbond.

Onceatomshavebondedtoformioniccompounds,theendings‘ide’and‘ate’areusedinnamingthem.(ateisusedifoxygenisalsopresent)i.e.Sodium+ChlorineàSodiumchloridePotassium+SulfuràPotassiumsulfideMagnesium+Sulfur(+oxygen)àMagnesiumsulfateIoniccompoundshaveaneutraloverallcharge,sothechargeofeachionicpartcanbeusedtoworkouttheformulaofthecompounds.Forexample:ChlorineàCl-

SodiumàNa+

MagnesiumàMg2+

Achlorineionhasa1negativecharge,andasodiumhasaonepositive. Thereforeyouneedoneofeachtobalancethemout.TheformulaisthereforeNaClAmagnesiumionhoweverhasa2+charge.TobalancethiswithChlorineonenegative,youwouldneed2chlorineions.TheformulawouldthereforebeMgCl2Groupsofatomscanalsohaveacharge,forexample‘NO3’hasa1-charge.Ioniccompoundscanformalatticestructure;wheremanyionsareorganisedintoaregulararrangement.Theyareheldtogetherwithstrongelectrostaticforces(ionicbonds)betweenpositiveandnegativelychargedions.Ioniccompoundshavehighmeltingpointsandhighboilingpoints,astheelectrostaticforcesbetweenionsareverystrong.Ioniccompoundsdonotconductelectricitywhensolid,astheelectronsarenotfreetomove,howevertheydoconductelectricitywhenmoltenordissolvedinanaqueoussolution.

CC5CovalentBondingAtomscanalsoshareelectronswithotheratomstofilltheiroutershell.Pairsofelectronsaresharedbetweentwoatomstoformmolecules.Thesharedelectronsaredrawninanoverlapbetweenthetwooutershells.Justtheoutershellscanbedrawn.Examplesinclude:H2 H2OCl2 CH4

Covalentmoleculeshavelowmeltingpointsandlowboilingpoints,astheforcesbetweenmoleculesareweak.Theyarealsopoorconductorsofelectricity.