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MeasurementandUnits
• SI – similar to (but not exactly the same as) the metric system
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Measurement and Units
• SI– similarto(butnotexactlythesameas)themetricsystem
PhysicalQuantity Nameofunit SymbolofUnitLength Meter mMass Kilogram kgTime Second sTemperature Kelvin KAmountofsubstance
Mole mol
Electriccurrent Ampere ALuminousintensity Candela cd
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Prefix MultipleTera(T) 1012
Giga(G) 109
Mega(M) 106
Kilo(k) 103
Centi(c) 10-2
Milli(m) 10-3
Micro(uorµ) 10-6
Nano(n) 10-9
Pico(p) 10-12
Femto(f) 10-15
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Moreonmeasurement
• Precision – how“close”experimentalvaluesaretoeachother(consistency)
• Accuracy – how“close”experimentalvaluesaretoa“true”or“accepted”value
• “closeness”canbemeasuredbyavarietyofstatisticaltechniques– mean,median,mode,standarddeviation,etc.
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Significantfigures
• Weliveintherealworld,notintheory!• Aidinreportingexperimentallymeasuredquantities–Anyinstrumentusedformeasurementwillhaveaspecifiedprecision(+/-)
–Weareallowedtoreportall known digitsandone unknown digit
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Significantfigures• Anynon-zerodigitissignificant(Ex.1234)• Zerossandwichedbetweendigitsaresignificant(Ex.1023)
• ZerostotheleftofadecimalareNOTsignificant(Ex.0.123)
• Zerostotheleftofthefirstnon-zerodigitareNOTsignificant(Ex.0.0000123)
• Zerostotherightofthelastnon-zerodigitaresignificant(Ex.0.123000)
• Ifthereisnodecimalpoint,zerosareNOTsignificant(Ex.100vs100.)
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Calculationsinvolvingsignificantfigures
• “Achainisonlyasstrongasitsweakestlink”• AdditionandSubtraction– usethenumberwiththeleastnumberofsignificantfiguresAFTERthedecimal(orleastnumberifthereisnodecimal)
• MultiplicationandDivision– usethenumberwiththeleastnumberofTOTALsignificantfigures
• Propagationoferror– roundonlyatthelaststepofamulti-stepcalculation(butkeeptrackofhowmanysigfigsthereshouldbeateachpoint)
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DimensionalAnalysisandUnitConversion
• Canbeusedasaproblem-solvingtool• Itisalwaysagoodideatoincludeunits,notjustnumbers!
• Ex.Howmanysecondsareinoneyear?
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ChemicalReactions(Equations)
• Note:Inthiscoursethephasesforeachchemicalreactionareomitted
• Example–2C2H6(g)+7O2(g)à 4CO2(g)+6H2O(l)willbewrittenas
–2C2H6 +7O2à 4CO2 +6H2O
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Neutralizations• Reactionofanacidwithabase
–Acid+Baseà Salt+Water• Overall/Completeformula/Molecularreaction:
–HCl(aq)+NaOH(aq)à NaCl(aq)+H2O(l)• However,weshouldreallyshowthisreactionasitwould“look”insolution
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Neutralizations• Ionicequation:
–H+(aq)+Cl-(aq)+Na+(aq)+OH-(aq)à Na+(aq)+Cl-(aq)+H2O(l)
(wateronlydissociatesaboutevery1in107 molecules)• Netionicequation:
–H+(aq)+OH-(aq)à H2O(l)–Spectatorions– identityisirrelevant,howevertheyarenecessaryforchargeneutrality
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Namingcompounds
• Usuallyputmetalfirst,thennonmetal(gofromlefttorightfromtheperiodictable)
• Exceptions– N,H,O• Name=firstelementsecondelement(-ide)• Prefixes– Ionicsubstancesgenerallyhavenoprefixes–Covalentsubstances– prefixesarealwaysusedforthe2nd element(evenifitonlyhasoneofthem)butareonlyusedforthe1st elementif>1
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Number Prefix1 Mono2 Di3 Tri4 Tetra5 Penta6 Hexa7 Hepta8 Octa9 Nona10 Deca
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IonicCompounds• Ions– atomsthathavegainedorlostelectrons(have+or– charge)–Canhaveverydifferentpropertiesthantheircorrespondingelements
• Cations- +charge(lostelectrons)–Usuallyoriginatefrommetals• Anions- - charge(gainedelectrons)–Usuallyoriginatefromnonmetals• Ionscanalsobepolyatomic (composedofmorethanoneatom)
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Determiningthechargeforanion
• ForGroupsIA-VIIIAthe“usual”chargeofanionisbasedonitsposition
–+1,+2,+3,+/-4,-3,-2,-1,0• ForGroupB(transitionmetals),usetheStocksystem–Romannumeralsrepresentcharges
–Ex.Fe(II)ion=Fe2+
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Oxyanions
• Containavaryingnumberofoxygenatomsaspartofapolyatomicion
Oxyanion NameClO- HypochloriteClO2
- ChloriteClO3
- ChlorateClO4
- Perchlorate
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FormulaUnit
• Strictlyspeaking,thistermshouldbeusedtodescribeioniccompounds
• Itrepresentsthesmallestcollectionofionsthatcombinetoformsomethingneutral
• Ex.NaCl,Al2O3
• Innamingformulaunits,prefixesareNOTused.
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Hydrates
• ChemicalsthatcontainH2Ointheirformula
• Thewatermoleculesareactuallyassociatedwiththecations/anionsinawell-definedway
• AprefixmustbeusedtoindicatethenumberofH2Omolecules
• Anhydrous(dry)– noH2Opresent
• Ex.CuSO4 vs.CuSO4.5H2O
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What’sanatommadeoutof?
• Allatomsarecomprisedofsubatomicparticles,whicharefundamental.
• Allsubatomicparticlesarecreatedequal– Theyareexactlythesame,eveniftheyarepresentindifferentatoms
• Threeareimportantforchemistry– Proton– Neutron– Electron
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J.J.Thomson(1897)
• Discoveryoftheelectron• (-)chargedparticleswereproduced,andtheybehavedexactlythesame,regardlessofthemetalthatwasused.
• Wasabletocalculatethem/zratio,-5.69X10-12 kg/C,butwasn’tabletogetindividualvaluesforthemassorcharge.
http://dbhs.wvusd.k12.ca.us/webdocs/AtomicStructure/Disc-of-Electron-Images.htmlhttp://www.makingthemodernworld.org.uk/icons_of_invention/science/1880-1939/IC.026/
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RobertMillikan(1909)• Measuredthevelocityofafallingoildropletinthepresence/absenceofamagnetic
field• Determinedthechargeonanelectron(-1.602X10-19 C)– Massofelectron=9.11X10-31 kg
http://www.juliantrubin.com/bigten/millikanoildrop.html
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ErnestRutherford(1911)
• a particle=• Mostparticlewentstraightthrough,butsomeweredeflected• Mostoftheatomisemptyspace,butallthe(+)chargeisconcentratedinthecenter(nucleus)
http://wps.prenhall.com/wps/media/objects/602/616516/Media_Assets/Chapter02/Text_Images/FG02_05.JPG
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Somedefinitions
• Isotope– same#ofprotons,butdifferent#ofneutrons• AtomicNumber(Z)– #ofprotons• MassNumber(A,M)- #ofnucleons(protonsandneutrons)
• AtomicMass– weightedaverageofallmassnumbers(weightedbyfractionalabundance)
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Theatomicmassunit(amu)
• Oneamu=1/12themassofoneatomofC-12(bydefinition)
• Thisisthebasicunitofmassforchemists,thoughitisn’tanSIunit
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Example
• Calculatetheatomicweightofcarbon.
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Solution
• Carbonexistsinthreeisotopicforms:12C,13Cand14C.• Therelativeabundancesoftheseisotopesareapproximately98.8%,1.1%and0.1%,respectively(thiscanbedeterminedbymassspectrometry)
• Thereforetheatomicweightwouldbe=12(0.988)+13(0.011)+14(.001)=12.011amu
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Gaschromatography– Massspectrometry(GC-MS)
• Usuallyrequiresionization
• Formchargedspecieswithanunpairedelectron(radical)
• Fragmentationpattern– Basedonbrokenchemicalbonds
– Eachpiece(fragment)hasacharacteristicm/zratio
• Molecularjigsawpuzzle
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Diagramofamassspectrometer
http://chemistry.umeche.maine.edu/CHY251/Ch13-Overhead4.html
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GC-MSinstruments
http://www.cooper.edu/~newmark/CH251/gcms.html
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Commonisotopicratios
• Ratioscantellyouwhichatomsyouhavepresent(bycomparingrelativeintensities)
Element Isotopes Abundance(%)
Hydrogen 1H,2H,3H 99.985,0.015,(0)
Carbon 12C,13C,14C 98.90,1.10,(0)
Nitrogen 14N,15N 99.63,0.37
Oxygen 16O,17O,18O 99.762,0.038,0.200
Chlorine 35Cl,37Cl 75.77,24.23
Bromine 79Br,81Br 50.69,49.31
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Example:Boron
http://www.chemguide.co.uk/analysis/masspec/elements.html
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Average atomic masses listed by IUPAC are based on a study of experimental results. Bromine has two isotopes 79Br and 81Br, whose masses (78.9183 and 80.9163 amu) and abundances (50.69% and 49.31%) were determined in earlier experiments. Calculate the average atomic mass of bromine based on these experiments.
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NuclearStability
• Nucleicanbepredictedtobestableorunstable“radioactive”basedonthenumberofnucleons(protonsandneutrons).
• GenerallyifZ>84(Po)thenuclidewillundergoradioactivedecay.AllelementswhereZ>92are“artificial”inthesensethattheyarenotnaturallyoccurring.
• For“small”nuclei,stableconfigurationsareachievedwhen(A-Z)/Zis1.
• For“large”nuclei,(A-Z)/Zis>1(1.2-1.4)
• “Magicnumbers”existwherenucleiareexceptionallystable:2,8,20,28,50,82,126.
http://www.kentchemistry.com/links/Nuclear/BandStability.htm
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RadioactiveDecay
• Inordertoachievestability,radioactivenucleiwilltypicallytry
tochangetheir(A-Z)/Zratiosotheycanfallinthebandof
stability.(a andb decays)• Itisalsopossibletobecomemorestableyetkeepthemassof
thenucleusthesame(g decay)• Otherpossibilitiesarefission (splittingofaheavynuclideintosmallernuclides)andfusion (joininglighternuclidesintoaheaviernuclide)
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a decay
• Lossofaheliumnucleus
– Resultsinejectionofpositiveparticles• Typicallyoccurswithheaviernuclei
• Example
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b decay
• Commonformedium-sizednuclides
• b- decay– lossofanelectron– Example
– Netconversionofaneutronintoaproton[(A-Z)/Ztoohigh]
• b+ decay(positronemission)– lossofanpositron– Example
– Apositronistheantiparticle ofanelectron• Electroncapture– gainofanelectron– Example
– Netconversionofaprotonintoaneutron[(A-Z)/Ztoolow]
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g decay
• Lossofahighenergyphoton
• Nochangeinatomicormassnumber
– Example
• Wecanthinkofthenucleonsasbeingfoundinvariousenergy
levels,justlikeelectrons
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Nuclearfission
• Artificialtransmutationprocessthatreleasesatremendous
amountofenergy
• Typicallyinitiatedbya“magicbullet”,commonlyaneutron:
• Noticethatforeveryoneneutronthatisused,threeneutrons
areproduced.Eachoftheseneutronscanthenbeusedfor
anotherfissionreaction,andsothereactionleadstoan
unstable(supercritical)situationsincethenumberofparticles
growsexponentially.Thisisknownasachainreaction.
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Lightandspectroscopy
• EMSpectrumhaswavesofvaryingfrequenciesandwavelengths
• E=hν =hc/λ• Spectroscopydealswiththeinteractionofmatterwithlight
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Atomiclinespectra• Acuvettefilledwithasampleisthenexposedtoabeamoflight.Sincelightofall
possiblewavelengthsareincident,itwasbelievedthatallpossiblewavelengthsshouldbeemitted,sothespectrumshouldbearainbow(continuousemission)
• However,somethingelsewasobserved…
• Balmer (1885) n=3,4,5…
http://www.faculty.virginia.edu/consciousness/new_page_6.htmhttp://www.astronomyknowhow.com/hydrogen-alpha.htm
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Asimple,yetrevolutionaryidea
• Planckproposedthatenergyisquantized:
E=hnh=Planck’sconstant=6.626*10-34 J*s
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“Old”QuantumMechanics
• Niels Bohr(1913)– Assumedthattheangularmomentum(nottheenergy!)oftheelectroninahydrogenatomisquantized
– Usedacombinationofclassicalphysicsandthisnewinterpretationforenergytoderive“orbits”,orenergylevels(verysimilartoaplanetarymodel)
– Thiswasbasedonwell-understoodfundamentalconstantsinphysics(andPlanck’sconstant)
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Atheoreticalexplanationofatomiclinespectra
• Photonsoflightareemittedwhenelectronsgofromahighertolowerenergylevel(oppositeistrueforabsorption)
• Becausetheenergylevelsarefixed,onlycertainwavelengthsoflightwillbeobserved
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Thegood,thebadandtheugly
• Thegood– Bohrwasabletocomeupwithatheoreticalmodelfortheenergylevelsinthehydrogenatomwhichaccountedfortheexperimentallyobservedlinespectra(Balmerseries)
• Thebad– Itonlyworkedforhydrogen!!!(andotherone-electronsystems)
• Theugly– Thenecessarymathematicsgetverydifficultveryquickly
– Multi-electronsystemsoftendon’thaveclosedformsolutions
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Quantumnumbers
• Principalquantumnumber(n)– n=1,2,3…– SameasBohr’senergylevels
– Indicateswhat“shell”theelectronisin• Angularmomentumquantumnumber(l)– l≤n-1– Ex.l=0à sorbital,l=1à porbital,l=2à dorbital,l=3à forbital
– Determinestheshape oftheorbital,or“subshell”
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Quantumnumbers
• Magneticquantumnumber(ml)– │ml│≤ l– Determinesthespatialorientation anddegeneracyoftheorbital– Ex.ifl=1(porbital)thenml =-1,0,1.Theseareusuallycalledpx,py,andpz (directionsdonotdirectlycorrespondtothesenumbers).Wecanalsoseewhytherearethreeporbitals,sincetherearethreeallowedvaluesforml.
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Subshell (orbital)shapes
• Orbitals
• Nodesarepossible– regionsofzeroprobabilityoffindingtheelectron
http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookchem1.html
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Quantumnumbers
• Spinquantumnumber(ms)– Unrelatedtotheotherthreequantumnumbers
– Unrelatedtospatialcoordinates– Eachelectronhasan“intrinsic”spincoordinate• Thereisnoclassicalanalog,butitbehavessimilartoangularmomentum
– ms =+/- ½(half-integer)
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• “Allelectronicwavefunctionsmustbeantisymmetricundertheinterchangeofanytwoelectrons”
• Itisimpossiblefortwoelectronsinthesameorbitaltohavethesamespin
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• Notwoelectronscanhaveidenticalquantumnumbers(inthesameatom)
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Consider the orbitals shown here in outline.
(a) What is the maximum number of electrons contained in an orbital of type (x)? Of type (y)? Of type (z)?
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Consider the orbitals shown here in outline.
(b) How many orbitals of type (x) are found in a shell with n = 2? How many of type (y)? How many of type (z)?
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Consider the orbitals shown here in outline.
(c) Write a set of quantum numbers for an electron in an orbital of type (x) in a shell with n = 4. Of an orbital of type (y) in a shell with n = 2. Of an orbital of type (z) in a shell with n = 3.
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Consider the orbitals shown here in outline.
(d) What is the smallest possible n value for an orbital of type (x)? Of type (y)? Of type (z)?
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Consider the orbitals shown here in outline.
(e) What are the possible l and ml values for an orbital of type (x)? Of type (y)? Of type (z)?
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Theperiodictable
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Main-groupelements(“theA-list”)
• Thevalence(outershell)consistsonlyofsandporbital
electrons
• Groupnumber=#ofelectronsinthevalenceshell(usingthe
olderRomannumeralsystem)
• Periodnumber=principalquantumnumber(n)
• sblock– alkalimetalsandalkaliearthmetals
• pblock– metals,metalloidsandnonmetals(including
halogensandnoblegases)
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Transitionmetals(“theB-team”)
• Containdandforbitals
• dblock- transitionmetals
• fblock– rareearth(lanthanide/actinide)
• Theseareconsidered“innershell”electrons
• Thehighestenergyelectronsareactuallyinashellwitha
smallervalueofnthatthatoftheoutermostshell(valence
shell)
– dblock– (n-1)– fblock– (n-2)
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PeriodicTrends
• Patternsthatemergeinchemicalandphysicalpropertieswhen
elementsarearrangedintheperiodictable
• Canusuallybeexplainedbythenumberofvalenceelectrons,
thenumberofcoreelectrons,andthenumberofprotons
(nuclearcharge)
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AtomicRadius
• Generallyatomicradiusdecreasesacrossaperiodand
increasesdownagroup
– Thetrendonlyworksformaingroupelements
http://edtech2.boisestate.edu/kilnerr/502/jigsaw.html
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AtomicRadius
• Group– increaseinthenumberofprincipalenergylevels
(greateraveragedistancethattheelectronisfromthe
nucleus)
• Period– increaseineffectivenuclearcharge(thenetcharge
thevalenceelectrons“feel”)
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EffectiveNuclearCharge(Zeff)
• Zeff ismeanttoincorporatetheshieldingeffectofcore(inner)
electrons
– Valenceelectronscanpenetrateinnershells(ex3dand4s)– Coreelectronsarenotallequallyeffectiveinshieldingvalenceelectrons
– Valenceelectronscanshieldeachother,thoughtheeffectisweak• Transitionmetalsinthesameperiodhavealmostthesame
radiussinceZeff isthesame
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IonicRadius
• Definedinasimilarfashiontoatomicradius(distancebetweentwoionsina
formulaunit)
• Metalstendtolosevalenceelectrons,sotheirhighestoccupiedprincipalenergy
leveldecreasebyone
– Ionicradiiformetalsaresmallerthanthoseofthecorrespondingatomicradii
• Nonmetalstendtogainvalenceelectrons,sotheirhighestoccupiedprincipal
energylevelremainsthesame,butthereisincreasedrepulsionamongthe
electronsinthatlevel
– Ionicradiifornonmetalsarelargerthanthoseofthecorrespondingatomicradii
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Inpictures
http://chemwiki.ucdavis.edu/Wikitexts/UC_Davis/UCD_Chem_124A%3A_Kauzlarich/ChemWiki
_Module_Topics/Periodic_Trends_in_Ionic_Radii
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IonizationEnergy
• Definedastheenergyrequiredtoremove anelectronfromthe
groundstate,inthegasphase
– A(g)à A+(g)+e-
• Thiscanberepeatedsuccessively(1st,2nd,3rd,etc.)
– Itgetsprogressivelyhardertoremoveelectronssincethespeciesisalready
charged
– Largejumpsoccurforagivenelementasyoubreakupanoctet(goingfrom
valenceelectronstocoreelectrons)
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IonizationEnergy
• Generallydecreasesasyougodownagroup
– Outermostelectronsare(onaverage)furtherawayfromthenucleus,sothereis
agreatershieldingeffect
• Generallyincreasesasyougoacrossaperiod
– Elementshaveagreatertendencytogainelectrons(ratherthanlose)
• Minoreffectscanbedueto
– whatsubshelltheelectronisin(s>p>d>fbecauseofenergy)
– Pairedvs.unpairedelectrons(unpaired>pairedbecauseofrepulsions)
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Inpictures
http://websites.pdesas.org/jvogus/2010/5/18/44324/page.aspx
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ElectronAffinity
• Definedastheenergyrequiredtoadd anelectrontothegroundstate,inthegasphase
– A(g)+e-à A-(g)
• Thishasthesamegeneraltrendasionizationenergy,although
itislessclear-cut
– Complicationsduetorepulsionsbetweentheincomingelectronand
theatomicelectrons
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Inpictures
http://www.angelo.edu/faculty/kboudrea/periodic/trends_electron_affinity.htm
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Electronegativity
• “Tendency”ofanelementtogainelectrons
• Paulingscale:
– (i-j)=bond-dissociationenergybetweeniandj– Fisarbitrarilygiventhemaximumvalueof4.0
• Alsofollowsthesamegeneraltrendasionizationenergyand
electronaffinity
2.... AEEI -
=c
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Inpictures
http://en.wikipedia.org/wiki/Electronegativity
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ChemicalPropertiesofElements
• Flametest
– Basedoncharacteristicabsorbanceoflightenergy
– Wavelengthemittedwillberelatedtotheenergygapbetweenelectroniclevels
– Usedtoidentifyvariousmetals
http://wesleydowler.com/?p=242
http://alchemist.edublogs.org/2008/11/17/which-ion-causes-the-color/
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Redoxreactions(anintroduction)
• Redoxreactionsinvolveasimultaneousreductionandoxidation.• Reduction– gainofelectrons
– oxidationnumberisdecreased
• Oxidation– lossofelectrons
– Oxidationnumberisincreased
• Disproportionation– redoxreactionwherethesamespeciesisboth
oxidizedandreduced.
– Ex.2H2O2 à 2H2O+O2
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Agents
• Reducingagent– causesareduction
– Getsoxidized– Usuallymetal
• Oxidizingagent– causesanoxidation
– Getsreduced– Usuallynonmetal
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Activityseries
• “Noble”metals(Cu,Ag,Hg,Au)
– can’tproduceH2
http://employees.csbsju.edu/hjakubowski/cla
sses/ch123/summer_chem/ch123OLSGMM04
05.htm
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ChemicalPropertiesofElements
• Reduction
– Reducingagentshaveatendencytoloseelectrons– Thispropertycanbecorrelatedwithionizationenergy,electronegativityandelectronaffinity
• MetalscanreactwithsourcesofH+ (acids,orevenwaterif
theyareactiveenough)togenerateionsandhydrogengas
• Mg+2H+ àMg2+ +H2
• Ca+2H2Oà Ca2+ +2OH- +H2
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ChemicalPropertiesofElements
• Oxidation
– Oxidizingagentshaveatendencytogainelectrons– Thispropertycanbecorrelatedwithionizationenergy,electronegativity,andelectronaffinity
• Cl2 +2I- à 2Cl- +I2 willoccursinceClatomshaveahigher
(morenegative)electronaffinitythanIatoms(-349kJ/molvs.-
295kJ/mol)
• I2 +Cl- à 2I- +Cl2 willNOToccur
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List the following ions in order of increasing radius: Li+, Mg2+, Br–, Te2–.
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Write the Lewis structure for SeCl3+.
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Explain why the H2O molecule is bent, whereas the BeH2
molecule is linear.
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Reactionsofalkalimetals
• Withhalogens(F2,Cl2,Br2,I2):– M+X2 àMX
• Withhydrogen:– M+H2 àMH
• With(excess)oxygen:– Li+O2 à Li2O(plussomeLi2O2)– Na+O2 à Na2O2 (plussomeNa2O)– M+O2 àMO2 (M=K,Rb,Cs)
• Withwater:– M+H2OàMOH+H2
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Reactionsofalkalineearthmetals
• Withhalogens(F2,Cl2,Br2,I2):–M+X2 àMX2
• Withnitrogen:–M+N2 àM3N2
• Withoxygen:–M+O2 àMO
• Withwater:–Mg+H2O(g)àMgO +H2
–M+H2OàM(OH)2 +H2(M≠Mg)
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PeriodicTrends
• Patternsthatemergeinchemicalandphysicalpropertieswhen
elementsarearrangedintheperiodictable
• Canusuallybeexplainedbythenumberofvalenceelectrons,
thenumberofcoreelectrons,andthenumberofprotons
(nuclearcharge)
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AtomicRadius
• Generallyatomicradiusdecreasesacrossaperiodand
increasesdownagroup
– Thetrendonlyworksformaingroupelements
http://edtech2.boisestate.edu/kilnerr/502/jigsaw.html
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IonizationEnergy
• Generallydecreasesasyougodownagroup
– Outermostelectronsare(onaverage)furtherawayfromthenucleus,sothereis
agreatershieldingeffect
• Generallyincreasesasyougoacrossaperiod
– Elementshaveagreatertendencytogainelectrons(ratherthanlose)
• Minoreffectscanbedueto
– whatsubshelltheelectronisin(s>p>d>fbecauseofenergy)
– Pairedvs.unpairedelectrons(unpaired>pairedbecauseofrepulsions)
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Overview- PeriodicTrendsinGroup13
• Bisanonmetal/metalloid– formscovalentbondsbutdisplays
electricalpropertiesofsemiconductors(diagonalrelationship
withSi)
• Alisametal/metalloid–formscovalentbondsbutcanalsolose
valenceelectronstoformions(Al3+)
• Ga – formsGa3+ionstoachievestableconfiguration([Ar]3d10)
• InandTl tendtoform+1ionsbecausetheylosethevalencep
electronbutNOTthevalenceselectrons(inertpair)
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Diagonalrelationships
• Oftenthe1st memberofagrouphas
propertiesthataredifferentfrom
theothermembersofthegroup,
butaresimilartothoseofthe2nd
memberoftheadjacentgroup
– Relativelyhighchargedensity
• Example:Li
• Li2CO3,LiF,LiOH andLi3PO4 are
muchlesssolublethanthe
correspondingsaltsoftheother
alkalimetals
– Li2CO3 andLiOH formLi2O
• Li+N2 à Li3N(otheralkalimetals
don’treact)
• Li+O2 à Li2O(otheralkalimetals
formperoxidesorsuperoxides)