Atoms,Molecules&Ions

CompoundsandMolecules Puresubstancescomposedoftwoormoredifferent

elementsarecalledcompounds.

Compoundshavedefinitepercentcompositionoftheircombiningelements.

Molecularcompounds

Standardcolorscheme

H2O2 CH3CH2Cl P4O10

CH3CH(OH)CH3 HCO2H

Somemolecules

S8

Inorganicmolecules

P4

Cyclo-S6

Cyclo-S12

z  Atomsofalmostallelementscangainorloseelectronstoformchargedspeciescalledions.

z  Compoundscomposedofionsareknownasioniccompounds.

u Metals tend to lose electrons to formpositivelychargedionscalledcations.

u  Non-metals tend to gain electrons toform negatively charged ions calledanions.

Ioniccompounds

ExtendedarrayofNa+andCl-ions

Sodiumchloride

SimplestformulaunitisNaCl

Halothane

C2HBrClF3

M(C2HBrClF3)=2MC+MH+MBr+MCl+3MF

(2×12.01)+1.01+79.90+35.45+(3×19.00)=

197.38g/mol

MolerationC/nhalothaneMassratiomC/mhalothane

ChemicalComposition

CalculatingtheMassPercentCompositionofaCompound

CalculatethemolecularmassM(C2HBrClF3)=197.38g/mol

Foronemoleofcompound,formulatethemassratioandconverttopercent:

%C =

(2 × 12.01)g

197.38g× 100% = 12.17%

%88.28%10038.197)00.193(%

%96.17%10038.19745.35%

%48.40%10038.19790.79%

%51.0%10038.19701.1%

%17.12%10038.197)01.122(%

=××=

=×=

=×=

=×=

=××=

ggF

ggCl

ggBr

ggH

ggC

CalculatingtheMassPercentCompositionofaCompound

1.  Chooseanarbitrarysamplesize(100g).2.  Convertmassestoamountsinmoles.3.  Writeaformula.4.  Convertformulatosmallwholenumbers.5.  Multiplyallsubscriptsbyasmallwholenumber

tomakethesubscriptsintegral.

5Stepapproach:

Empiricalformula

DeterminingtheEmpiricalandMolecularFormulasofaCompoundfromItsMassPercentComposition.

Dibutyl succinate is an insect repellent used againsthousehold ants and roaches. Its composition is62.58%C,9.63%Hand27.79%O. Itsexperimentallydeterminedmolecularmass is 230u. What are theempirical and molecular formulas of dibutylsuccinate?

Dibutyl succinate is an insect repellent used againsthousehold ants and roaches. Its composition is62.58%C,9.63%Hand27.79%O. Itsexperimentallydeterminedmolecularmass is 230u. What are theempirical and molecular formulas of dibutylsuccinate?

Step1:Determinethemassofeachelementina100gsample.

C62.58g O27.79gH9.63g

DeterminingtheEmpiricalandMolecularFormulasofaCompoundfromItsMassPercentComposition.

DeterminingtheEmpiricalandMolecularFormulasofaCompoundfromItsMassPercentComposition.

Step2:Convertmassestoamountsinmoles.

Step3:Writeatentativeformula.

Step4:Converttosmallwholenumbers.

�

nC = 62.58gC×1molC

12.011gC= 5.210molC

nH = 9.63gH×1molH

1.008gH= 9.55molH

nO = 27.79gO×1molO

15.999gO= 1.737molO

C5.21H9.55O1.74

C2.99H5.49O

DeterminingtheEmpiricalandMolecularFormulasofaCompoundfromItsMassPercentComposition.

Step5:Converttoasmallwholenumberratio.

Multiply× 2togetC5.98H10.98O2

TheempiricalformulaisC6H11O2

Step6:Determinethemolecularformula.Empiricalformulamassis115u.Molecularformulamassis230u.

ThemolecularformulaisC12H22O4

Combustionanalysis

Metalstendtoloseelectrons.

NaDNa++e-

Non-metalstendtogainelectrons.

Cl+e-DCl-

Reducingagents Oxidizingagents

WeusetheOxidationStatetokeeptrackofthenumberofelectronsthathavebeengainedorlostbyanelement.

OxidationStates

1.  Theoxidationstate(OS)ofanindividualatominafreeelementis0.2.  ThetotaloftheOSinallatomsin:

i.  Neutralspeciesis0.ii.  Ionicspeciesisequaltothechargeontheion.

3.  Intheircompounds,thealkalimetalsandthealkalineearthshaveOSof+1and+2respectively.

4.  IncompoundstheOSoffluorineisalways–15.  Incompounds,theOSofhydrogenisusually+16.  Incompounds,theOSofoxygenisusually–2.7.  Inbinary(two-element)compoundswithmetals:

i.  HalogenshaveOSof–1,ii.  Group16haveOSof–2andiii.  Group15haveOSof–3.

RulesforOxidationStates

Anions(-Q):Groups15,16,17(VA,VIA,VIIA)Cations(+Q):Groups1,2,3(IA,IIA,IIIA)

AssigningOxidationStates.

Whatistheoxidationstateoftheunderlinedelementineachofthefollowing?a)P4;b)Al2O3;c)MnO4

-;d)NaH

a)  P4 is an element. P OS = 0 .

b)  Al2O3: O is –2. O3 is –6. Since (+6)/2=(+3), Al OS = +3.

c)  MnO4-: net OS = -1, O4 is –8. Mn OS = +7.

d)  NaH: net OS = 0, rule 3 beats rule 5, Na OS = +1 and H OS = -1.

PeriodicTrendsInOxidationStateshttps://www.youtube.com/watch?v=JTFYVoV9rsg

Trivialnamesareusedforcommoncompounds.Asystematicmethodofnamingcompoundsisknownasasystemofnomenclature.

OrganiccompoundsInorganiccompounds

NamingCompounds

BinaryCompoundsofMetalsandNonmetals

NaCl = sodium chloride

“ide”endingelectrically

neutral

MgI2 = magnesium iodide

Al2O3 = aluminum oxide

Na2S = sodium sulfide

InorganicNomenclature

nameisunchanged

MolecularcompoundsusuallywritethepositiveOSelementfirst. HClhydrogenchloride

mono 1 penta 5

di 2 hexa 6

tri 3 hepta 7

tetra 4 octa 8

Somepairsformmorethanonecompound

BinaryCompoundsofTwoNon-metals

NamingBinaryCompoundsoftheNon-metalsNamedinorderofincreasinggroupnumber

N2O4 Dinitrogentetroxide

Sulfurhexafluoride

N2O Dinitrogenoxide

SF6

Emphasizethefactthatamoleculeisanacidbyalteringthename.

HCl hydrogen chloride hydrochloric acid

HF hydrogen fluoride hydrofluoric acid

AcidsproduceH+whendissolvedinwater.

Theyarecompoundsthationizeinwater.

BinaryAcids

Polyatomicionsareverycommon.Hereareafew:

ammonium ion NH4+ acetate ion C2H3O2

-

carbonate ion CO32- hydrogen carbonate HCO3

-

hypochlorite ClO- phosphate PO43-

chlorite ClO2- hydrogen phosphate HPO4

2-

chlorate ClO3- sulfate SO4

2-

perchlorate ClO4- hydrogensulfate HSO4

-

PolyatomicIons

Gaining(anion)andLosing(cation)ElectronstoattainInertgaselectronic

structure

IonicBonding:

When an atom gainselectrons it becomesananion.Anion are larger thantheneutralatom.

Whenanatom loseselectrons itbecomesacation.Cations are smallerthan the neutralatom.

Theattractiveforcebetween+and-chargesiscalledacoulombicattraction

Forceofattraction=

1× 2

2Q QK

d

Predicttheionicbondstrengthofthefollowingionicbonds.

Consideracationandananion

NaCl

NaCl

MgClCl

MgCl2

Howtowriteformulasforionicbinarycompounds

1.Identifyions

2.“Cross”charges

3.Writeformula1 2

ChargeisConserved:Positivechargesequalthenegativeones!

NamingIonicCompounds

Cationsarenamedasthemetal+“ion”

Na+=sodiumion

Multichargedions

StockSystem Metal(ChargeinRomanNumerals)

“ion”Cu1+ Cu2+

Copper(I)ion Copper(II)ion

MgBr2 Magnesiumbromide

Fe2O3 Iron(III)oxide

Ca3(PO4)2 Calciumphosphate

NamingIonicCompounds

MoreExamples

Mg(NO3)2

FeO

CuBr2

NaHCO3

CompoundsandMolecules

Somecompoundsarecomposedofmolecules.

Sharingelectronstoattaininertgaselectronconfigurations.E

d

CovalentBonding:

OrganiccompoundsaboundinnatureFats,carbohydratesandproteinsarefoods.

Propane,gasoline,kerosene,oil.

Drugsandplastics

Carbonatomsformchainsandringsandactas

theframeworkofmolecules.

NamingOrganicCompounds

MolecularStructure

Thearrangementofatomsinamolecule

Isomers:

SamenumberofconstituentatomsBUT

differentarrangements.

Visualiza

tionsofsom

ehydrocarbo

ns

Functio

nalG

roup

s:

CarboxylicAcid

Functio

nalG

roup

s:

Alcoho

l

Isomerism

Structural

Stereo

Optical

Geometrical

Positional

Functional

Chain

ChainIsomers

n-pentane

2-methylbutane

2,2-dimethylpropane

C5H12

Positio

nalIsomers:

C 7H 7OH

PositionalIsomers

Propan-1-olo

Propan-2-olo

C3H7OH

Positio

nalIsomers:

C 7H 7OH

2-Methylphenol

4-Methylphenol

3-Methylphenol

Functio

nalIsomers:

C 2H 6O

Ethanol

Methoxymethane

Alcoholshavethehydroxylgroup,–OHEthershavethefunctionalgroupR–O–R'

Functio

nalIsomers:

C 3H 6O

Propanal

Aldehydes and ketones have the carbonyl groupC=O. InaldehydesC isattachedeitherto1or2Hatoms; in ketones C is attached to two carbonatoms.

Propanone

Isomerism

Structural

Stereo

Optical

Geometrical

Positional

Functional

Chain

GeometricalIsomers

Geometrical isomerism is an example ofstereo-isomerism. This occurs whensubstances have the same molecularformula,butadifferentarrangementoftheiratomsinspace.

Geometrical isomerism can happen if: i)  There is a C=C bond in the molecule ii)  The molecule has a ring iii)  The molecule has a >C=N bond

GeometricalIsomersC4H8

Cis-But-2-ene Trans-But-2-ene

trans-Pt(NH3)2Cl2 cis-Pt(NH3)2Cl2

GeometricalIsomers

Pt(NH3)Cl3

Noisomers

GeometricalIsomers

cis-Pt(NH3)Cl2Br trans-Pt(NH3)Cl2Br

Twoisomers

GeometricalIsomers

ClN

Cl

Pt

N

ClCl

ClN

Cl

Pt

Cl

NCl

transTwoisomers

cis

GeometricalIsomers

Cl N

Cl

Pt

Cl

N N

Cl N

Cl

Pt

N

NCl

facTwoisomers

mer

GeometricalIsomers

OpticalIsomers

Optical isomerism is an example of stereo-isomerism. It occurs when substances have thesame molecular and structural formula, but onecannot be superimposed on the other. Thedifferentformsarecalledenantioners.

opticalisomerism

non-superimposablemirrorimages

OpticalIsomers

Optical isomers can occur when there is anasymmetric carbon atom; i.e. a C atombondedtofourdifferentgroups.

La chiralità di una molecola o di un oggetto assume rilevanzasolamente quando quell’oggetto interagisce con un’altro chirale. Diconseguenza, una coppia di enantiomeri possiede le seguentiproprietà:§  stessopuntodiebollizioneedifusione§  stessadensità

§  stessopesomolecolare

§  stessasolubilitàneisolventiachirali

§  rotazionispecificheuguali,madisegnoopposto:fannoruotareilpianodellalucepianopolarizzatadellostessonumerodigradi,maindirezionidiverse:(-)levorotatorioo(+)destrorotatorio

§  attivitàbiologichediverse,poichénegliorganismisonocoinvoltiinreazioniconaltremolecolechirali

La prima apparizione sul mercato fu con il prodotto commercialedenominato Grippex (talidomide in associazione con altri principiattivi) prodotta dalla ditta tedesca Chemie Grünenthal. Il Grippexsomministrato in formasperimentaleper il trattamentodi infezionirespiratorienonebbealcunsuccessoeilsuoimpiegoterapeuticofusospeso.

Nel 1954, dopo anni di ulteriori prove e ricerche, la ChemieGrünenthal,depositòedottenne ilbrevettoperContergan,abaseditalidomide,il“miracoloso”farmacoanti-nauseaesedativo.

La(R)-talidomideèunsonniferocompletamenteinnocuola (S)-talidomidehaproprietàteratogene(da“teratos”,mostro=chegeneramalformazioni).