experiment #4. elements and compounds. -...

Experiment#4.ElementsandCompounds.

GoalsTopracticenamingandclassifyingelementsandcompoundsBackgroundPropertiesofElementsElements on the periodic table can be classified as metals, non-metals or metalloids. The zigzag line on the tableseparates themetals from the nonmetals. Themetalsmake up over 75%of knownelements and are foundon thelowerleftsideofthetable.Metalsareshiny,goodconductorsofheatandelectricity,andmalleable(canbepoundedintosheets).Nonmetalsarefoundontheupperrightcorneroftheperiodictable.Nonmetalsaredull,poorconductorsof heat and electricity, and brittle. Metalloids, or semi-metals are located on the zigzag line of the periodic table.Aluminum touches the line, but is considered a metal. Metalloids have properties that are intermediate betweenmetalsandnonmetals.Theytendtobeshiny,brittle,andaverageconductorsofheatandelectricity.

Elementscanalsobecategorizedbytheirgroup.Thewordperiodicreferstothefactthatpropertiesofelementsinthetablerepeat.Elementsarearrangedincolumns,orgroups,ontheperiodictablewhereallelementsinthegrouphavesimilarproperties.Forinstance,allelementsingroup8A,thenoblegases,areunreactive.Elementsingroup1A,thealkalimetals,arehighlyreactiveandproducehydrogenwhenmixedwithwater.Othernamedgroupsincludethealkalineearthmetals(2A),thehalogens(7A),andthetransitionmetals(elementsintheblockbetween2Aand3A).

CompoundsWhen two or more elements come together, a chemical compound is formed. In this lab you will practice

namingcompounds.NamingCompounds

Manyeverydayandcompoundshavecommonnames.Forexample,wateristhecommonnameforH2O,bakingsoda is the common name for NaHCO3. However, there are too many compounds (80 million +) for memorizingcommonnamestobepracticalsochemistshavedevelopedrulesfornaming.Inthisexerciseyouwillpracticerulesfornamingsimpleionicandcovalentcompoundsandlearntopredicttheratiosthatchemicalscombineinbasedontheirioniccharge.

IonicCompoundswithMetalChargesthatDoNotVary

Simple ioniccompoundsare formed fromametalandnon-metal ions. Themetal is thecation,orpositivelycharged ion and the nonmetal is the anion, or negatively charged ion. In the chemical formula, the cation is alwayswrittenfirstandtheanioniswrittensecond.Cationswithchargesthatdon’tvaryincludeGroup1Aalkalimetals,whichalwaysform1+cationsandGroup2Aalkalineearthmetalswhichalwaysform2+cations,andGroup3Ametals,whichalwaysform3+ions.

Toname this typeof ionic compound, the cation getswritten first using its full elementname. The anion is

writtensecondusingthestemofitselementnameandaddingan“ide”ending.Forinstance,fluorinebecomesfluorideandoxygenbecomesoxide.

Examples: NaCl sodiumchloride MgBr2magnesiumbromide

Ionic compounds are electronically neutral, meaning the charges on the anions andcationsbalancetozero.Todetermineaformulafromachemicalname,youmustfirstdeterminethechargesontheionsinthecompoundandthenfigureouthowmanyofeachareneededtobalancethecharges.ForinstancecalciumchlorideismadeofCa2+andCl-ions.ForthechargestobalancethereneedstobetwoCl-ions,thereforetheformulaisCaCl2.

IonicCompoundswithMetalChargesthatVary

Somemetalscanformionswithdifferentcharges.Forinstance,ironinioniccompoundsisfoundasbothFe2+andFe3+.Metalswithchargesthatvaryincludemosttransitionmetals(zinc,cadmiumandsilverareexceptions)plustinand lead. Sincemore than one charge is possible,more than one chemical formula is possible. Iron can form twocompoundswithchlorine:Fe2+formsFeCl2,Fe3+formsFeCl3.Thesetwodifferentcompoundshavedifferentphysicalandchemical properties. For example, FeCl2 has amelting point of 306° C,while FeCl3 melts at 677° C. Therefore,wecannotsimplycallbothcompounds“ironchloride.”

Whennamingcompoundswithmetalthathavevariablecharge,aromannumeralinparenthesesiswrittenafterthemetalnameandindicatedthechargeonthemetal. For instance,Fe2+ iscallediron(II)andFe3+ iscallediron(III).Theanioniswrittenasthe“ide”formoftheelement.

When starting with the formula, the charge of themetal has to be deducedfrom theanion charge. The formulaCuO indicatesoneatomofoxygen carryinga2-charge. In order for the charges to sum to zero, the copper atom must have a 2+.Thereforethenameiscopper(II)oxide.

The formula SnCl4 has 4 chloride ions, each with a 1- charge, so the totalnegativechargeis4-.Thechargeonthetinmustbe4+,sothecompoundisnamedtin(IV)chloride.

IonicCompoundswithPolyatomicIons

Polyatomicionsareionscomposedoftwoormorecovalentlybondedatomsthatcanbethoughtofasasingleunitcarryingacharge. Ioniccompoundsthathavethreeormoreelementsaregenerallycomposedofametalcationandpolyatomicanion.Ammonium(NH4

+)istheonlycommonpolyatomiccation.Thenames,formulasandchargesofpolyatomicionsmustbememorized(seetableofcommonpolyatomicionsbelow).Ioniccompoundswithpolyatomicionsgetnamed in thesamewayasType Iand IIbinary ioniccompoundswith thenameof thepolyatomic ion in theplaceoftheanionname.Ifmorethanonepolyatomicionisneededtobalancethecharges,thewholeiongetsputinparentheses.Examples: Li2CO3 lithiumcarbonate Pb(NO3)2 lead(II)nitrate NH4Cl ammoniumchloride

Ionswith1-charge Ionswith2-chargeNO2

- Nitrite SO32- Sulfite

NO3- Nitrate SO4

2- SulfateClO2

- Chlorite CO32- Carbonate

ClO3- Chlorate

CN- Cyanide OH- Hydroxide Ionswith3-chargeHCO3

- Hydrogencarbonate PO33- Phosphite

PO43- Phosphate

Ionswith1+charge NH4

+ Ammonium

Covalent(Molecular)Compounds

Covalentcompoundsaremadeoftwoormorenon-metals,asopposedtoametalandanon-metal.Thesystemfor naming covalent compounds is different from the one for ionic compounds and it is important to keep the twosystemsseparate.

Tonameacovalentcompound,thefirstelementiswrittenasitselementname,thesecondelementiswrittenasits“ide”form,andbothelementsgetaprefixthatindicatesthenumberofeachelementinacompound.Iftheprefixofthefirstelementismono,theprefixisdropped.

Examples: P2S5 diphosphorouspentasulfide

N2O dinitrogenmonoxide NO2 nitrogendioxide

Prefixes1 mono-2 di-3 tri-4 tetra-5 penta-

6 hexa-7 hepta8 octa-9 nona-10 deca-

Materials: elementvials samplesofCu,Zn,C,Si conductivityprobe Procedure

A.PropertiesofElements 1. Observethepropertiesofvariouselementssamplesinthelabeledbottles.Completelyfillouttheelement

propertiestableinthedatasheet.Ifanelementdoesnotbelongtoanamedgroup,writethegroupnumber(ex4A)inthelastcolumn.

2. Touchthetwowireendsoftheconductivityprobetothefourelementsintheconductivitytable.IftheLEDlights,thecircuitwascompletedmeaningthattheelementconductselectricity.

B.NamingCompounds3. Fill in the tables with the missing name, formula or ion. Refer to naming rules in the lab background or your

textbook.

Name_________________________

TeamName______________________

CHM101Lab–ElementsandCompounds–GradingRubricToparticipateinthislabyoumusthavesplash-proofgoggles,propershoesandattire.

Criteria Pointspossible Pointsearned

LabPerformance

Printedlabhandoutandrubricwasbroughttolab

3

Safetyandproperwastedisposalproceduresobserved

2

Followedprocedurecorrectlywithoutdependingtoomuchoninstructororlabpartner

3

Workspaceandglasswarewascleanedup

1

LabReport

PartA(elements)

3

PartA(conductivity)

2

PartB(Ionic)

4

PartB(Covalent)

2

Total

20

Subjecttoadditionalpenaltiesatthediscretionoftheinstructor.

ElementsandCompounds

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A.PropertiesofElements

Element Symbol AtomicNumber

Color ShinyorDull? Metal,nonmetalormetalloid?

GroupName(ornumberifnone)

Aluminum

Bismuth

Carbon

Copper

Helium

Iodine

Magnesium

Mercury

Nickel

Oxygen

Silicon

Sulfur

Tin

Zinc

Element Metal,nonmetalormetalloid? Conductive? Doesresultfityourexpectations?Silicon

Copper

Sulfur

Zinc

ElementsandCompounds

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B.CompletethefollowingtableforioniccompoundsFormula cation anion Name

Al2O3 Al3+ O2- aluminumoxide

Cu(NO3)2 Cu2+ NO3- copper(II)nitrate

iron(III)phosphide

Pb2+ Br-

Li2S

potassiumcarbonate

Ni(OH)3

Mg2+ N3-

cesiumnitrite

CoF2

tin(IV)oxide

(NH4)2SO4

calciumcyanide

CompletethefollowingtableofcovalentcompoundsFormula Name

NO2 nitrogendioxide

SO3

diphosphoroustrisulfide

CBr4

oxygendifluoride

IBr