Chemical compoundsChemical compounds

TypesTypesFormulasFormulasNamesNames

Learning objectivesLearning objectives

Describe the octet ruleDescribe the octet rule Predict number of valence electrons on atomPredict number of valence electrons on atom Predict ionic chargesPredict ionic charges Predict composition of simple ionic compoundsPredict composition of simple ionic compounds Predict which element combinations result in Predict which element combinations result in

covalent bondingcovalent bonding Describe difference between ionic and covalent Describe difference between ionic and covalent

bondsbonds Describe differences between ionic and covalent Describe differences between ionic and covalent

compoundscompounds

Compounds rather than elementsCompounds rather than elements

Most atoms are more stable when bonded Most atoms are more stable when bonded to other atomsto other atoms

Compounds contain two or more elementsCompounds contain two or more elements Distinguish between ionic compounds and Distinguish between ionic compounds and

molecular compoundsmolecular compounds

Ionic versus molecularIonic versus molecular

Ionic compoundsIonic compounds Consist of ions (NaCl)Consist of ions (NaCl) Always metal + nonmetalAlways metal + nonmetal Infinite latticeInfinite lattice

Molecular compoundsMolecular compounds Consist of molecules (COConsist of molecules (CO22)) Finite sizeFinite size Always nonmetals or metalloidsAlways nonmetals or metalloids

Electrolytes and nonelectrolytesElectrolytes and nonelectrolytes

An electrolyte is something that conducts An electrolyte is something that conducts electricity in solution – produces ionselectricity in solution – produces ions

All soluble ionic compounds are All soluble ionic compounds are electrolyteselectrolytes

Molecular compounds except acids and Molecular compounds except acids and bases are nonelectrolytesbases are nonelectrolytes

Electrolyte and nonelectrolyteElectrolyte and nonelectrolyte

Ionic compound in solution produces ions - Ionic compound in solution produces ions - is an electrolyteis an electrolyte

Molecular compound in solution as Molecular compound in solution as molecules – is nonelectrolyte (or weak molecules – is nonelectrolyte (or weak electrolyte in some cases)electrolyte in some cases)

Ionic compounds Ionic compounds alwaysalways contain a contain a metal and a non-metalmetal and a non-metal

Comparing propertiesComparing properties

Rules to predict ion chargeRules to predict ion charge

CationCation Charge = group numberCharge = group number

AnionAnion Charge = - (8 - group number)Charge = - (8 - group number)

Practice with a few examplesPractice with a few examples

Composition depends on ionic Composition depends on ionic charge (group number)charge (group number)

Charges must balance: compounds are Charges must balance: compounds are neutral – ions are chargedneutral – ions are charged

Total cation charges = total anion chargesTotal cation charges = total anion charges One CaOne Ca2+ 2+ two Ftwo F--

Brief introduction to formulaeBrief introduction to formulae Overall charge must be neutralOverall charge must be neutral Formula contains metal ion first, nonmetal ion secondFormula contains metal ion first, nonmetal ion second Coefficient of metal = charge on nonmetalCoefficient of metal = charge on nonmetal Coefficient of nonmetal = charge on metalCoefficient of nonmetal = charge on metal x and y are shown with lowest common denominator in most cases. x and y are shown with lowest common denominator in most cases.

Calcium oxide is CaO not CaCalcium oxide is CaO not Ca22OO22

A Bx y

x-y+

Polyatomic ionsPolyatomic ions

Group of atoms with an ionic chargeGroup of atoms with an ionic charge Usually different elementsUsually different elements Except OExcept O22

2-2- or Hg or Hg222+2+

Oxoanion has element surrounded by O Oxoanion has element surrounded by O atomsatoms

Polyatomic ions of the main groupPolyatomic ions of the main group

--ateate ending refers to ion ending refers to ion with more O atoms (SOwith more O atoms (SO44

2-2-))

--iteite refers to ion with refers to ion with fewer O atoms (SOfewer O atoms (SO33

2-2-))

In a group, charge on ion In a group, charge on ion is the sameis the same

With more than two:With more than two: PerPer refers to ion with most refers to ion with most

O atoms (ClOO atoms (ClO44--))

HypoHypo refers to ion with least refers to ion with least O atoms (ClOO atoms (ClO--))

Other important polyatomic ionsOther important polyatomic ions

• Hydrogen Hydrogen carbonate or carbonate or bicarbonate has Hbicarbonate has H++ addedadded

• Cyanide is CNCyanide is CN--

• Acetate is CHAcetate is CH33COCO22--

• Ammonium is NHAmmonium is NH44++

The The Name GameGame

Naming conventions are different for ionic Naming conventions are different for ionic and covalent compoundsand covalent compounds

Let’s play the name game to find outLet’s play the name game to find out

Distinguishing ion charge in the Distinguishing ion charge in the namename

Follow rules of ionic Follow rules of ionic compound names compound names with one addition:with one addition:

Identify ion charge by Identify ion charge by Roman numeral after Roman numeral after metal namemetal name

Potential confusion Potential confusion caused by old caused by old names:–names:–icic and – and –ousous endingsendings

Molecular compoundsMolecular compounds

Don’t contain ionsDon’t contain ions Often have different compounds for the Often have different compounds for the

same elementssame elements

Names and prefixes with molecular Names and prefixes with molecular compoundscompounds

Distinguish in name Distinguish in name by using prefixesby using prefixes

Used for every Used for every element in formula element in formula except when first one except when first one is singleis single

AcidsAcids

Acids are molecular compounds that produce HAcids are molecular compounds that produce H++ ions in solutionions in solution

HCl HCl → H→ H++(aq) + Cl(aq) + Cl--(aq)(aq) HH++ exists as H exists as H33OO++

Mineral acids:Mineral acids: HClHCl HNOHNO33

HH22SOSO44

Carboxylic acidsCarboxylic acids

Important class of acids in nature are carboxylic Important class of acids in nature are carboxylic acids:acids:

Acetic acidAcetic acid Citric acidCitric acid Lactic acidLactic acid Malic acidMalic acid Formic acidFormic acid

All contain -COOHAll contain -COOH

Identifying acids: it can be confusingIdentifying acids: it can be confusing

Although all acids contain HAlthough all acids contain H Not all compounds containing H are acids!Not all compounds containing H are acids! Mineral acids have H at beginning:Mineral acids have H at beginning:

HNOHNO33, HCl, H, HCl, H22SOSO44

Not always with organic acids:Not always with organic acids: CHCH33COOH (also written HCHCOOH (also written HCH33COOCOO

BasesBases

Bases generate OHBases generate OH-- in solution: in solution:

NaOH NaOH → Na→ Na++(aq) + OH(aq) + OH--(aq)(aq) Mineral bases contain OHMineral bases contain OH- - ions and metal ionsions and metal ions

NaOH, Ba(OH)NaOH, Ba(OH)22

Bases like NHBases like NH33 react with H react with H22O:O:

NHNH33 + H + H22O → NHO → NH44++ + OH + OH--

Naming acidsNaming acids

Acid and base strengthAcid and base strength

Strong acids and bases are completely ionized in Strong acids and bases are completely ionized in HH22O:O:

HCl, HNOHCl, HNO33, NaOH, Ba(OH), NaOH, Ba(OH)22

Weak acids and bases are partially ionized in Weak acids and bases are partially ionized in HH22O:O:

HNOHNO22, CH, CH33COOH, NHCOOH, NH33

Summary of namingSummary of naming