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General Physical ScienceGeneral Physical Science

Chapter 12Chapter 12

Chemical BondingChemical Bonding

The Law of Conservation of The Law of Conservation of

MassMass

�� No detectable change No detectable change

in the total mass in the total mass

occurs during a occurs during a

chemical reactionchemical reaction

ExampleExample

�� In a chemical reaction involving carbon In a chemical reaction involving carbon

and oxygen, laboratory measurements and oxygen, laboratory measurements

showed that the complete burning in showed that the complete burning in

oxygen of 4.09 g of carbon produced oxygen of 4.09 g of carbon produced

15.00 g of carbon dioxide as the only 15.00 g of carbon dioxide as the only

product. How many grams of oxygen product. How many grams of oxygen

reacted?reacted?

�� 15.00 g = 4.09 g + x g15.00 g = 4.09 g + x g

�� x = 15.00 x = 15.00 -- 4.09 = 10.91 g oxygen4.09 = 10.91 g oxygen

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The Law of Conservation of The Law of Conservation of

MassMass

�� Learning Goal:Learning Goal:

�� State and use the Law of Conservation of State and use the Law of Conservation of

Mass.Mass.

�� Questions: 1Questions: 1--33

�� Exercise: 1, 3Exercise: 1, 3

Law of Definite ProportionsLaw of Definite Proportions

�� Different samples of a pure compound Different samples of a pure compound always contain the same elements in the always contain the same elements in the same proportion by mass.same proportion by mass.

�� Atomic Mass (AM)Atomic Mass (AM)�� The number below the elemental symbol.The number below the elemental symbol.

�� Formula Mass (FM)Formula Mass (FM)�� Sum of the atomic massesSum of the atomic masses

�� AKA formula weight/molecular weightAKA formula weight/molecular weight

ExampleExample

�� Calculate the formula mass of PbCrOCalculate the formula mass of PbCrO44, the , the

bright yellow compound used in paint for bright yellow compound used in paint for

the yellow lines on streets.the yellow lines on streets.

�� Atomic MassesAtomic Masses

�� PbPb = 207.2; Cr = 52.0; O = 16.0= 207.2; Cr = 52.0; O = 16.0

�� 207.2 + 52.0 + (4 x 16.0)207.2 + 52.0 + (4 x 16.0)

�� 323.2323.2

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Percent by MassPercent by Mass

�� Since all compounds have the same Since all compounds have the same

elemental makeup, we should be able to elemental makeup, we should be able to

calculate how much of each element is calculate how much of each element is

present (by mass)present (by mass)

�� (Mass element / FM) * 100%(Mass element / FM) * 100%

ExampleExample

�� Calculate the percent by mass for carbon Calculate the percent by mass for carbon

and oxygen in dry ice (COand oxygen in dry ice (CO22))

�� Formula Mass = 12.0 + 16.0*2 = 44.0Formula Mass = 12.0 + 16.0*2 = 44.0

�� Formula Mass Percent CarbonFormula Mass Percent Carbon

�� (12.0 / 44.0) * 100% = 27.3%(12.0 / 44.0) * 100% = 27.3%

�� Percent OxygenPercent Oxygen

�� (16.0*2 / 44.0) * 100% = 72.7%(16.0*2 / 44.0) * 100% = 72.7%

�� Note that 27.3 + 72.7 = 100.0Note that 27.3 + 72.7 = 100.0

Limiting ReactantLimiting Reactant

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Law of Definite ProportionsLaw of Definite Proportions

�� Learning GoalsLearning Goals

�� Calculate the formula masses of compounds.Calculate the formula masses of compounds.

�� State and use the Law of Definite Proportions.State and use the Law of Definite Proportions.

�� Questions: 4 Questions: 4 -- 66

�� Exercises: 5Exercises: 5--11 odd11 odd

DaltonDalton’’s Atomic Theorys Atomic Theory�� 3 postulates3 postulates

�� Each element is composed of small indivisible Each element is composed of small indivisible

particles called atoms which are identical for particles called atoms which are identical for

that element but different from atoms of other that element but different from atoms of other

elementselements

�� Chemical combination is the bonding of a Chemical combination is the bonding of a

definite, small number of atoms of each of the definite, small number of atoms of each of the

combining elements to make one molecule of combining elements to make one molecule of

the formed compound.the formed compound.

�� No atoms are gained, lost, or changed in No atoms are gained, lost, or changed in

identity during a chemical reaction: they are identity during a chemical reaction: they are

just rearranged.just rearranged.

DaltonDalton’’s Atomic Theorys Atomic Theory

�� Explains Law of Conservation of MassExplains Law of Conservation of Mass

�� If we rearrange atoms we still have the same If we rearrange atoms we still have the same

amount of amount of ‘‘stuffstuff’’

�� Explains Law of Definite ProportionsExplains Law of Definite Proportions

�� Test with similar compoundsTest with similar compounds

�� CO and COCO and CO22

�� For a fixed amount of C, the ratio of the masses of For a fixed amount of C, the ratio of the masses of

oxygen in CO and COoxygen in CO and CO22 is a small whole number.is a small whole number.

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DaltonDalton’’s Atomic Theorys Atomic Theory

�� Learning GoalLearning Goal

�� State the postulates of DaltonState the postulates of Dalton’’s atomic theory.s atomic theory.

�� Questions: 7 Questions: 7 -- 88

Ionic BondingIonic Bonding

�� Valence electrons control chemical Valence electrons control chemical

behavior.behavior.

�� Noble gases do not react.Noble gases do not react.

�� Noble gas configuration must be stable!Noble gas configuration must be stable!

�� Octet RuleOctet Rule

�� Atoms try to surround themselves with 8 Atoms try to surround themselves with 8

electronselectrons

Ionic BondingIonic Bonding

�� Octet RuleOctet Rule

�� 2 methods2 methods

�� Transfer of electronsTransfer of electrons

�� Sharing of electronsSharing of electrons

�� Ionic compounds are formed by the Ionic compounds are formed by the

transfer of electrons from one species transfer of electrons from one species

(metal) to another species (nonmetal)(metal) to another species (nonmetal)

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Formation of Formation of NaClNaCl

Lewis SymbolsLewis Symbols

�� G. N. LewisG. N. Lewis

�� Uses dots to show valence electronsUses dots to show valence electrons

�� Dots on each of the four sides of the symbolsDots on each of the four sides of the symbols

�� All single dots before any dots are pairedAll single dots before any dots are paired

IonsIons

�� CationsCations

�� positively charged ionspositively charged ions

�� For the representative elements, the group For the representative elements, the group

number will equal the charge on the ion.number will equal the charge on the ion.

�� AnionsAnions

�� negatively charged ionsnegatively charged ions

�� charge = group number charge = group number -- 88

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Ionic CompoundsIonic Compounds

�� Ions are held together by electrostatic Ions are held together by electrostatic

attraction between the ions.attraction between the ions.

�� Formula for an ionic compound represents Formula for an ionic compound represents

the smallest ratio of the smallest ratio of cationscations and anions to and anions to

give a give a ‘‘neutralneutral’’ speciesspecies

�� in reality there are no in reality there are no ‘‘moleculesmolecules’’ of ionic of ionic

compoundscompounds

�� exist in a large matrixexist in a large matrix

Ionic CompoundsIonic Compounds

ExampleExample

�� Write the formula for calcium phosphate, Write the formula for calcium phosphate,

the major component in bones.the major component in bones.

�� Calcium; Group 2 (metal)Calcium; Group 2 (metal)

�� charge will be +2charge will be +2

�� PhosphatePhosphate

�� polyatomic ion; charge is polyatomic ion; charge is --33

�� CaCa33(PO(PO44))22..

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Electrical ConductionElectrical Conduction

�� Electricity can be conducted by ions.Electricity can be conducted by ions.

�� Ionic solid Ionic solid -- no electrical conductionno electrical conduction

�� Ions are locked into positionIons are locked into position

�� Ionic liquid Ionic liquid -- will conduct electricitywill conduct electricity

�� Most ionic compounds melt at temps well Most ionic compounds melt at temps well

in excess of 300in excess of 300OOCC

�� Soluble ionic compound conducts elec.Soluble ionic compound conducts elec.

�� Ions free to move in solutionIons free to move in solution

Stock System NomenclatureStock System Nomenclature

�� Applies to metals that form ions with more Applies to metals that form ions with more than one chargethan one charge�� Typically transition elementsTypically transition elements

�� Some heavier postSome heavier post--transition representative transition representative metals alsometals also

�� Name of metal (charge of ion) anionName of metal (charge of ion) anion�� iron(II) chlorideiron(II) chloride

�� copper(I) nitratecopper(I) nitrate

Ionic BondingIonic Bonding

�� Learning GoalsLearning Goals�� Write formulas for ionic compoundsWrite formulas for ionic compounds

�� Describe the characteristics of ionic Describe the characteristics of ionic compoundscompounds

�� Name compounds containing a metal that Name compounds containing a metal that forms more than one ion.forms more than one ion.

�� Questions: 19 Questions: 19 -- 2121

�� Exercises: 13 Exercises: 13 -- 19 odd19 odd

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Covalent BondingCovalent Bonding

�� Sharing of electronsSharing of electrons

�� Stable covalent bonds will give all atoms a Stable covalent bonds will give all atoms a noble gas configurationnoble gas configuration�� Shared electrons are counted twice!Shared electrons are counted twice!

�� HH22, Cl, Cl22, H, H22O, NHO, NH33, CH, CH44..

�� Multiple bonding between 2 atomsMultiple bonding between 2 atoms�� Double bondsDouble bonds

�� Triple BondsTriple Bonds

Covalent Bond in HydrogenCovalent Bond in Hydrogen

Polyatomic IonsPolyatomic Ions

�� Contain both ionic and covalent Contain both ionic and covalent

characteristicscharacteristics

�� Atoms in a polyatomic ion are held together Atoms in a polyatomic ion are held together

with covalent bondswith covalent bonds

�� To get enough electrons to To get enough electrons to ‘‘shareshare’’ and and

complete all octets the polyatomic anions complete all octets the polyatomic anions

need need ‘‘extraextra’’ electrons electrons -- gives negative chargegives negative charge

�� This then forms ionic bond with metals.This then forms ionic bond with metals.

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Prediction of Bond TypePrediction of Bond Type

�� Only nonmetals Only nonmetals -- covalentcovalent

�� Metals/nonmetals (generally) ionicMetals/nonmetals (generally) ionic

�� Metals/polyatomic ions ionicMetals/polyatomic ions ionic

�� Gases, liquids, low mp solids covalentGases, liquids, low mp solids covalent

�� Conduct electric current when molten (but Conduct electric current when molten (but

not when solid) ionicnot when solid) ionic

Polar Covalent BondingPolar Covalent Bonding

�� Unequal sharing of electronsUnequal sharing of electrons

�� Leads to partial negative and partial positive Leads to partial negative and partial positive

on covalent molecule.on covalent molecule.

�� DipoleDipole

�� ElectronegativityElectronegativity

�� LinusLinus PaulingPauling

�� Tendency of an element to attract an electron Tendency of an element to attract an electron

in a bond.in a bond.

ElectronegativityElectronegativity

�� Increases for representative elements Increases for representative elements

from bottom left to top right.from bottom left to top right.

�� Excludes noble gasesExcludes noble gases

�� Noble gases donNoble gases don’’t form bonds!t form bonds!

�� Fr lease electronegativeFr lease electronegative

�� F most electronegativeF most electronegative

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Polar MoleculesPolar Molecules

�� Must have two thingsMust have two things�� Polar bondPolar bond

�� Occurs when elements of different Occurs when elements of different electronegativitieselectronegativities are bonded.are bonded.

�� Essentially, different nonmetalsEssentially, different nonmetals

�� Non symmetric arrangementNon symmetric arrangement�� Symmetry Symmetry -- tugtug--ofof--war with no winnerwar with no winner

�� Polarity drives solubilityPolarity drives solubility�� Likes dissolve likesLikes dissolve likes

Covalent BondingCovalent Bonding

�� Learning GoalsLearning Goals

�� Write molecular formulas and Lewis structures Write molecular formulas and Lewis structures

for covalent compoundsfor covalent compounds

�� Describe the characteristics of covalent Describe the characteristics of covalent

compoundscompounds

�� Questions: 22 Questions: 22 -- 3131

�� Exercises: 21 Exercises: 21 -- 29 odd29 odd

Hydrogen BondingHydrogen Bonding

�� Solubility of table saltSolubility of table salt�� ionion--dipole interactiondipole interaction

�� molecules have dipolemolecules have dipole--dipole interactiondipole interaction�� energy that holds the molecule togetherenergy that holds the molecule together

�� higher the energy, higher the boiling pointhigher the energy, higher the boiling point

�� Hydrogen bondHydrogen bond�� Special type of dipoleSpecial type of dipole--dipole interaction.dipole interaction.

�� Large value for dipoleLarge value for dipole

�� small size of hydrogensmall size of hydrogen

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Hydrogen BondingHydrogen Bonding

�� Occurs when H bonded to F, O, or NOccurs when H bonded to F, O, or N

�� Hydrogen bonding about 5Hydrogen bonding about 5--10% of 10% of

strength of covalent bondstrength of covalent bond

�� Typical molecular interaction less than 1% Typical molecular interaction less than 1%

of covalent bond!of covalent bond!

�� Causes ice to be less dense than waterCauses ice to be less dense than water

�� Leads to life on Earth!Leads to life on Earth!

�� Holds DNA togetherHolds DNA together

�� Leads to life on Earth!Leads to life on Earth!

Hydrogen BondingHydrogen Bonding

�� Learning GoalsLearning Goals

�� Predict when hydrogen bonding will occurPredict when hydrogen bonding will occur

�� Describe how hydrogen bonding affects a Describe how hydrogen bonding affects a

compoundcompound’’s properties.s properties.

�� Questions: 32, 33Questions: 32, 33

�� Key Terms; Matching, Multiple Choice, and Key Terms; Matching, Multiple Choice, and

FillFill--inin--thethe--Blank Questions; Visual Blank Questions; Visual

Connection and Applying your KnowledgeConnection and Applying your Knowledge

General Physical ScienceGeneral Physical Science

Chapter 12Chapter 12

Chemical BondingChemical Bonding