Ch2 z53 particles

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Chapter 2Chapter 2

Atoms, Molecules, and IonsAtoms, Molecules, and Ions pp

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HistoryHistory GreeksGreeks Democritus and Leucippus - Democritus and Leucippus - atomosatomos Aristotle- elements.Aristotle- elements. AlchemyAlchemy 1660 - Robert Boyle- experimental 1660 - Robert Boyle- experimental

definition of element.definition of element. Lavoisier- Father of modern chemistry.Lavoisier- Father of modern chemistry. He wrote the book.He wrote the book.

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LawsLaws Conservation of MassConservation of Mass Law of Definite Proportion - compounds Law of Definite Proportion - compounds

have a constant composition.have a constant composition. They react in specific ratios by mass.They react in specific ratios by mass. Multiple Proportions - When two elements Multiple Proportions - When two elements

form more than one compound, the ratios of form more than one compound, the ratios of the masses of the second element that the masses of the second element that combine with one gram of the first can be combine with one gram of the first can be reduced to small whole numbers.reduced to small whole numbers.

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What?!What?! Water has 8 g of oxygen per g of hydrogen.Water has 8 g of oxygen per g of hydrogen. Hydrogen peroxide has 16 g of oxygen per Hydrogen peroxide has 16 g of oxygen per

g of hydrogen.g of hydrogen. 16/8 = 2/116/8 = 2/1 Small whole number ratios.Small whole number ratios.

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ProofProof Mercury has two oxides. One is 96.2 % Mercury has two oxides. One is 96.2 %

mercury by mass, the other is 92.6 % mercury by mass, the other is 92.6 % mercury by mass.mercury by mass.

Show that these compounds follow the law Show that these compounds follow the law of multiple proportion.of multiple proportion.

Speculate on the formula of the two oxides.Speculate on the formula of the two oxides.

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Dalton’s Atomic TheoryDalton’s Atomic Theory1)1) Elements are made up of atomsElements are made up of atoms

2)2) Atoms of Atoms of eacheach element are identical. element are identical. Atoms of Atoms of differentdifferent elements are different. elements are different.

3)3) CompoundsCompounds are formed when atoms are formed when atoms combine. Each compound has a specific combine. Each compound has a specific number and kinds of atom.number and kinds of atom.

4)4) Chemical reactions are rearrangement of Chemical reactions are rearrangement of atoms. Atoms are not created or atoms. Atoms are not created or destroyed.destroyed.

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Gay-Lussac- under the same conditions of Gay-Lussac- under the same conditions of temperature and pressure, compounds temperature and pressure, compounds always react in whole number ratios by always react in whole number ratios by volume.volume.

Avagadro - interpreted that to mean . . . Avagadro - interpreted that to mean . . . at the same temperature and pressure, equal at the same temperature and pressure, equal

volumes of gas contain the same number of volumes of gas contain the same number of particles.particles.

(called (called Avagadro’s HypothesisAvagadro’s Hypothesis))

A Helpful ObservationA Helpful Observation

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Figure 2.4Figure 2.4Representation of some of Gay-Lussac’s Experimental Representation of some of Gay-Lussac’s Experimental

Results on Combining Gas VolumesResults on Combining Gas Volumes

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Figure 2.5 Figure 2.5 Representation of Combining Gases at the Representation of Combining Gases at the

Molecular LevelMolecular Level

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Early Experiments to determine Early Experiments to determine what an atom waswhat an atom was

J. J. Thomson- used Cathode ray tubesJ. J. Thomson- used Cathode ray tubes

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Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

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Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

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Passing an electric current makes a beam Passing an electric current makes a beam appear to move from the negative to the appear to move from the negative to the positive end.positive end.

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

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Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric field By adding an electric field

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Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric field, he found that By adding an electric field, he found that the moving pieces were negative the moving pieces were negative

+

-

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Thomsom’s ModelThomsom’s Model Found the electron.Found the electron. Couldn’t find positive Couldn’t find positive

(for a while). (for a while). Said the atom was like Said the atom was like

plum pudding.plum pudding. A bunch of positive A bunch of positive

stuff, with the stuff, with the electrons able to be electrons able to be removed. removed.

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Millikan’s ExperimentMillikan’s Experiment

Oil

Atomizer

Oil droplets

Telescope

-

+

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Millikan’s ExperimentMillikan’s Experiment

X-rays

X-rays give some electrons a charge.

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Millikan’s ExperimentMillikan’s Experiment

Some drops would hoverFrom the mass of the drop and the charge on the plates, he calculated the mass of an electron

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Figure 2.10Figure 2.10Diagram of the Millikan Apparatus Diagram of the Millikan Apparatus

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RadioactivityRadioactivity Discovered by accidentDiscovered by accident BequerelBequerel Three types Three types

– Alpha- helium nucleus (+2 charge, large Alpha- helium nucleus (+2 charge, large mass)mass)

– Beta - high speed electronBeta - high speed electron

– Gamma - high energy lightGamma - high energy light

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Rutherford’s ExperimentRutherford’s Experiment Used uranium to produce alpha particles.Used uranium to produce alpha particles. Aimed alpha particles at gold foil by Aimed alpha particles at gold foil by

drilling hole in lead block.drilling hole in lead block. Since the mass is evenly distributed in Since the mass is evenly distributed in

gold atoms alpha particles should go gold atoms alpha particles should go straight through.straight through.

Used gold foil because it could be made Used gold foil because it could be made atoms thin.atoms thin.

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Lead block

Uranium

Gold Foil

Florescent Screen

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What he expected

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Because

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Because, he thought the mass was evenly distributed in the atom.

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What he got

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How he explained it

+

Atom is mostly emptyAtom is mostly empty Small dense,Small dense,

positive piecepositive pieceat center.at center.

Alpha particlesAlpha particlesare deflected byare deflected by it if it if they get closethey get close enough. enough.

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+

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Figure 2.12Figure 2.12Rutherford’s Experiment on Rutherford’s Experiment on particle particle

Bombardment of Metal FoilBombardment of Metal Foil

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Figure 2.13Figure 2.13 Expected and Actual Results of Expected and Actual Results of

Rutherford’s ExperimentRutherford’s Experiment

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Modern ViewModern View The atom is mostly The atom is mostly

empty space.empty space. Two regionsTwo regions Nucleus - protons Nucleus - protons

and neutrons.and neutrons. Electron cloud - Electron cloud -

region where you region where you mightmight find an find an electron.electron.

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Sub-atomic ParticlesSub-atomic Particles Z - atomic number = number of protonsZ - atomic number = number of protons Z determines type of atom.Z determines type of atom. A - mass number = number of protons + A - mass number = number of protons +

neutrons.neutrons. Number of protons = number of electrons Number of protons = number of electrons if if

neutral.neutral.

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The Mass and Change of the The Mass and Change of the Electron, Proton, and NeutronElectron, Proton, and NeutronThe Mass and Change of the The Mass and Change of the

Electron, Proton, and NeutronElectron, Proton, and Neutron

Particle Mass (kg) Charge

Electron 9.11 ¥ 10- 31 1-

Proton 1.67 ¥ 10- 27 1+

Neutron 1.67 ¥ 10- 27 0

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SymbolsSymbols

XA

Z

Na23

11

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Chemical BondsChemical Bonds The forces that hold atoms together.The forces that hold atoms together. Covalent bonding - sharing electrons.Covalent bonding - sharing electrons. Makes molecules.Makes molecules. Chemical formula - the number and type of Chemical formula - the number and type of

atoms in a molecule. atoms in a molecule. CC22HH66 - 2 carbon atoms, 6 hydrogen atoms, - 2 carbon atoms, 6 hydrogen atoms,

Structural formula shows the connections, Structural formula shows the connections, but not necessarily the shape.but not necessarily the shape.

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H

H

H H

H

HC C

There are also other models that attempt to There are also other models that attempt to show three dimensional shape.show three dimensional shape.

Ball and stick or space-filling.Ball and stick or space-filling.

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IonsIons Atoms or groups of atoms with a charge.Atoms or groups of atoms with a charge. Cations - positive ions - get by Cations - positive ions - get by losinglosing

electrons(s).electrons(s). Anions- negative ions - get by Anions- negative ions - get by gaininggaining

electron(s).electron(s). Ionic bonding - held together by the Ionic bonding - held together by the

opposite charges.opposite charges. Ionic Ionic solidssolids are called salts. are called salts.

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Polyatomic IonsPolyatomic Ions Groups of atoms that have a charge.Groups of atoms that have a charge. Yes, you have to memorize them.Yes, you have to memorize them. See list on page 66See list on page 66

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Periodic TablePeriodic Table

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MetalsMetals ConductorsConductors Lose electronsLose electrons Malleable and ductileMalleable and ductile

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NonmetalsNonmetals BrittleBrittle Gain electronsGain electrons Covalent bondsCovalent bonds

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Semi-metals or MetalloidsSemi-metals or Metalloids

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Alkali Metals

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Alkaline Earth Metals

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Halogens

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Transition metals

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Noble Gases

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Inner Transition Metals

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+1+2 -1-2-3

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Naming compoundsNaming compounds Two typesTwo types IonicIonic - metal with non metal or with - metal with non metal or with

polyatomic ions.polyatomic ions. CovalentCovalent- we will just learn the rules for - we will just learn the rules for

non-metals combined with non-metal.non-metals combined with non-metal.

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Ionic compoundsIonic compounds If the If the cationcation is monoatomic - Name the metal is monoatomic - Name the metal

(cation) just write the name.(cation) just write the name. Include a Roman numeral to indicate the oxidation Include a Roman numeral to indicate the oxidation

state if the cation (metal) has more than one.state if the cation (metal) has more than one. If the cation is polyatomic - name it.If the cation is polyatomic - name it. If the anion is monoatomic - name it but change If the anion is monoatomic - name it but change

the ending to the ending to –ide.–ide. If the anion is poly atomic - just name itIf the anion is poly atomic - just name it Practice.Practice.

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Figure 2.22Figure 2.22 Common Cations and Anions Common Cations and Anions

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Ionic CompoundsIonic Compounds Have to know what ions they formHave to know what ions they form Get from periodic table, polyatomic, or figure outGet from periodic table, polyatomic, or figure out CaSCaS

KK22SS

AlPOAlPO44

KK22SOSO44

FeSFeS CoICoI33

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Figure 2.23Figure 2.23Flowchart Flowchart for Naming for Naming Binary Binary CompoundsCompounds

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Ionic CompoundsIonic Compounds FeFe22(C(C22OO44))

MgOMgO MnOMnO

KMnOKMnO44

NHNH44NONO33

HgHg22ClCl22

CrCr22OO33

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Ionic CompoundsIonic Compounds KClOKClO44

NaClONaClO33

YBrOYBrO22

Cr(ClO)Cr(ClO)66

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Naming Covalent CompoundsNaming Covalent Compounds Two words, with prefixesTwo words, with prefixes Prefixes tell you how many.Prefixes tell you how many. mono, di, tri, tetra, penta, hexa, septa, nona, mono, di, tri, tetra, penta, hexa, septa, nona,

decadeca First element whole name with the First element whole name with the

appropriate prefix, except monoappropriate prefix, except mono Second element, Second element, -ide -ide ending with appropriate ending with appropriate

prefixprefix PracticePractice

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COCO22

CO CO CClCCl44

NN22OO44

XeFXeF66

NN44OO44

PP22OO1010

Naming Covalent CompoundsNaming Covalent Compounds

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Writing FormulasWriting Formulas Two sets of rules, ionic and covalentTwo sets of rules, ionic and covalent To decide which to use, decide what the To decide which to use, decide what the

first word is.first word is. If is a metal or polyatomic use ionic.If is a metal or polyatomic use ionic. If it is a non-metal use covalent.If it is a non-metal use covalent.

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Ionic FormulasIonic Formulas Charges must add up to zero.Charges must add up to zero. Get charges from periodic table, name of Get charges from periodic table, name of

metal ion, or memorized from the list.metal ion, or memorized from the list. Use parentheses to indicate multiple Use parentheses to indicate multiple

polyatomics.polyatomics.

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Ionic FormulasIonic Formulas Sodium nitrideSodium nitride Sodium - Na is always +1Sodium - Na is always +1 nitride - ide tells you it comes from the nitride - ide tells you it comes from the

periodic tableperiodic table nitride is Nnitride is N-3-3

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Ionic FormulasIonic Formulas Sodium nitrideSodium nitride Sodium - Na is always +1Sodium - Na is always +1 Nitride - ide tells you it comes from the Nitride - ide tells you it comes from the

tabletable nitride is Nnitride is N-3-3 Doesn’t add up to zero (if 1:1 ratio).Doesn’t add up to zero (if 1:1 ratio).

Na+1 N-3

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Ionic FormulasIonic Formulas Sodium nitrideSodium nitride sodium- Na is always +1sodium- Na is always +1 nitride - ide tells you it comes from the tablenitride - ide tells you it comes from the table nitride is Nnitride is N-3-3 Doesn’t add up to zeroDoesn’t add up to zero So, need 3 Na (“Cross the charges”)So, need 3 Na (“Cross the charges”)

Na+1 N-3 Na3N

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Ionic CompoundsIonic Compounds Sodium sulfiteSodium sulfite calcium iodidecalcium iodide Lead (II) oxide Lead (II) oxide Lead (IV) oxideLead (IV) oxide Mercury (I) sulfideMercury (I) sulfide Barium chromateBarium chromate Aluminum hydrogen sulfateAluminum hydrogen sulfate Cerium (IV) nitriteCerium (IV) nitrite

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Covalent compoundsCovalent compounds The name tells you how to write the The name tells you how to write the

formulaformula duhduh Sulfur dioxideSulfur dioxide difluorine monoxidedifluorine monoxide nitrogen trichloridenitrogen trichloride diphosphorus pentoxidediphosphorus pentoxide

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Chemical Naming pp:

P = cation

Q = anion

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AcidsAcids Substances that produce HSubstances that produce H++ ions when ions when

dissolved in water.dissolved in water. All acids begin with H.All acids begin with H. Two types of Two types of inorganicinorganic acids: acids: OxyacidsOxyacids Non-oxyacidsNon-oxyacids OrganicOrganic acids have -COOH group acids have -COOH group

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Naming acidsNaming acids If the formula has oxygen in itIf the formula has oxygen in it write the name of the anion, but change write the name of the anion, but change

– ate to -ic acidate to -ic acid– ite to -ous acidite to -ous acid

Hint: “m -ic- e” or more than a “m -ous- e”Hint: “m -ic- e” or more than a “m -ous- e” Watch out for sulfWatch out for sulfururic and sulfic and sulfururousous

HH22CrOCrO44

HMnOHMnO44

HNOHNO22

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Naming acidsNaming acids If the acid doesn’t have oxygenIf the acid doesn’t have oxygen add the prefix hydro-add the prefix hydro- change the suffix -ide to -ic acidchange the suffix -ide to -ic acid HClHCl HH22SS

HCNHCN

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Formulas for acidsFormulas for acids Working backwards from names.Working backwards from names. If it has hydro- in the name it has no oxygenIf it has hydro- in the name it has no oxygen Anion ends in -ideAnion ends in -ide No hydro, anion ends in -ate or -ite (and it No hydro, anion ends in -ate or -ite (and it

is an oxyacid)is an oxyacid) Write anion and add enough H to balance Write anion and add enough H to balance

the charges.the charges.

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Figure 2.25 Flowchart for Naming Acids Figure 2.25 Flowchart for Naming Acids pp

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Formulas for acidsFormulas for acids hydrofluoric acidhydrofluoric acid dichromic aciddichromic acid carbonic acidcarbonic acid hydrophosphoric acidhydrophosphoric acid hypofluorous acidhypofluorous acid perchloric acidperchloric acid phosphorous acid phosphorous acid

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HydratesHydrates Some salts trap water crystals when they Some salts trap water crystals when they

form crystals.form crystals. These are hydrates.These are hydrates. Both the name and the formula need to Both the name and the formula need to

indicate how many water molecules are indicate how many water molecules are trapped.trapped.

In the name we add the word hydrate with a In the name we add the word hydrate with a prefix that tells us how many water prefix that tells us how many water molecules. molecules.

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HydratesHydrates pp

In the formula you put a dot and then write In the formula you put a dot and then write the number of molecules.the number of molecules.

Calcium chloride dihydrate = CaClCalcium chloride dihydrate = CaCl222222 Chromium (III) nitrate hexahydrate = Chromium (III) nitrate hexahydrate =

Cr(NOCr(NO33))33 6H 6H22O O