12.-The-Alkali-Metals-v1.0

©BoardworksLtd20071of392of39©BoardworksLtd2007©BoardworksLtd20073of39Wherearethealkalimetals?Theelementsingroup1,ontheleftoftheperiodictable,arecalledthealkalimetals.Thesemetalsareallveryreactiveandarerarelyfoundinnatureintheirelementalform.lithiumsodiumpotassiumrubidiumcaesiumfranciumFrCsRbKNaLi©BoardworksLtd20074of39Whatarethealkalimetals?©BoardworksLtd20075of39Whyaretheycalledthe‘alkalimetals’?Thealkalimetalsaresoreactivethat,aselements,theyhavetobestoredinoil.Thisstopsthemreactingwithoxygenintheair.Thealkalimetalsareunlikemostothermetals,whichareusuallyhardanddense.Theelementsingroup1alsoreactwithwaterandformalkalinecompounds.Thisiswhytheyarecalledalkalimetals.Alkalimetalsaresoftenoughtobecutwithaknife,andthemostcommonalkalimetals,lithium,sodiumandpotassium,allfloatonwater.©BoardworksLtd20076of39Whatistheelectronstructureofalkalimetals?Thealkalimetalsallhaveoneelectronintheiroutershell.lithium2,1sodium2,8,1potassium2,8,8,1Theyarefoundingroup1oftheperiodictable.Theyhavesimilarphysicalandchemicalproperties.Thismeansthat:Theycanreadilylosetheoutershellelectrontoformpositiveionswitha+1chargeandafulloutershell.©BoardworksLtd20077of39Howdoyouidentifyalkalimetals?8of39©BoardworksLtd2007©BoardworksLtd20079of39Whatarethepropertiesofthealkalimetals?Thecharacteristicpropertiesofthealkalimetalsare:Theyareshiny.Thisisonlyseenwhenalkalimetalsarefreshlycut.Theyaregoodconductorsofheatandelectricity.Theyaresoftandcanbecutbyaknife.Softnessincreasesgoingdownthegroup.Theyhavealowdensity.Lithium,sodiumandpotassiumfloatonwater.Theyhavelowmeltingandboilingpoints.Thesepropertiesmeanthatthealkalimetalsaredifferenttotypicalmetals.However,alkalimetalsdoalsosharesomepropertieswithtypicalmetals:©BoardworksLtd200710of39Whatisthetrendindensity?Thealkalimetalsgenerallybecomemoredensegoingdownthegroup,butthetrendisnotperfectbecausepotassiumislessdensethansodium.Waterhasadensityof1g/dm3.ElementDensity(g/dm3)lithiumpotassiumsodiumrubidiumcaesium0.530.970.861.531.87Whichelementsingroup1willfloatonwater?©BoardworksLtd200711of39Whatarethetrendsindensity?©BoardworksLtd200712of39Whatisthetrendinmeltingandboilingpoint?Themeltingpointsandboilingpointsofalkalimetalsdecreasegoingdownthegroup.ElementMeltingpoint(°C)lithiumpotassiumsodiumrubidiumcaesium18198643928Boilingpoint(°C)Themeltingandboilingpointsdecreasegoingdowngroup1becausetheatomsgetlarger.Ineachmetallicstructure,theattractionbetweenthepositivemetalionsandthedelocalizedseaofelectronsgetsweakerandsotheybecomeeasiertomelt,andtoboil.1342883760686671©BoardworksLtd200713of39Whatarethetrendsinmeltingpoint?©BoardworksLtd200714of39Whatarethetrendsinboilingpoint?©BoardworksLtd200715of39Propertiesofalkalimetalsquiz16of39©BoardworksLtd2007©BoardworksLtd200717of39Howdothealkalimetalsreactwithoxygen?Allalkalimetalsreactwithoxygenintheairtoformmetaloxides.Thisproducesalayerofdulloxideonthesurfaceofthemetal,calledtarnish.Thespeedwithwhichalkalimetalsreactwithoxygenintheairincreasesgoingdownthegroup:Whyarealkalimetalsstoredinoil?lithium–tarnishesslowlysodium–tarnishesquicklypotassium–tarnishesveryquickly.Theoilpreventsthemfromreactingwithoxygenandtarnishing.©BoardworksLtd200718of39Whatarethewordandchemicalequationsforthereactionthatcausessodiumtotarnish?Whatistheequationforthereactionwithoxygen?Thereactionbetweenanalkalimetalandoxygenisanexampleofanoxidationreaction:alkalimetal+oxygenalkalimetaloxide4Na(s)+O2(g)2Na2O(s)sodium+oxygensodiumoxideThewordandchemicalequationsforthereactionbetweenlithiumandoxygenare:4Li(s)+O2(g)2Li2O(s)lithium+oxygenlithiumoxide©BoardworksLtd200719of39Howdothealkalimetalsreactwithwater?©BoardworksLtd200720of39Allthealkalimetalsreactvigorouslywithwater.Thereactionproducesagasthatignitesalightedsplintwithasqueakypop.Whatisthisgas?Whatdoesthereactionwithwaterproduce?Itisanexothermicreactionasitreleasesalotofheat.Whengreenuniversalindicatorisaddedtothereactionmixture,itturnspurple.Whatdoesthistellyouabouttheproductsofthisreaction?Thereactionwithwaterbecomesmorevigorousasyougodownthegroup.©BoardworksLtd200721of392M(s)+2H2O(l)2MOH(aq)+H2(g)alkalimetal+wateralkalimetal+hydrogenhydroxideThisreactioncreatesalkalinehydroxideions.Thegeneralequationforthereactionbetweenanalkalimetalreactingwithwateris:Whatistheequationforthereactionwithwater?Thisiswhythegroup1elementsarecalledthealkalimetals.©BoardworksLtd200722of39Howdoeslithiumreactwithwater?Lithiumistheleastreactiveofthealkalimetals.2Li(s)+2H2O(l)2LiOH(aq)+H2(g)lithium+waterlithium+hydrogenhydroxideWhenaddedtowater,itfizzesandmovesaroundslowlyacrossthesurfaceofthewater.Whatistheequationforthisreaction?©BoardworksLtd200723of39Howdoessodiumreactwithwater?Whenaddedtowater,sodiumfizzesmorethanlithium,andmovesquicklyacrossthesurfaceofthewater.2Na(s)+2H2O(l)2NaOH(aq)+H2(g)sodium+watersodium+hydrogenhydroxideWhatistheequationforthisreaction?Thehydrogensometimescatchesfirebecauseoftheheatfromthereaction.Thesodiummeltsasitreacts,anditbecomessphericalandshiny,likeaballbearing.©BoardworksLtd200724of39Howdoespotassiumreactwi