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Chemistry C3 Topic 1
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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.